sec(1) General Commands Manual sec(1)
NAME
sec - simple event correlator
SYNOPSIS
sec [--conf=<file pattern> ...]
[--input=<file pattern>[=<context>] ...]
[--input-timeout=<input timeout>]
[--timeout-script=<timeout script>]
[--reopen-timeout=<reopen timeout>]
[--check-timeout=<check timeout>]
[--poll-timeout=<poll timeout>]
[--blocksize=<io block size>]
[--bufsize=<input buffer size>]
[--evstoresize=<event store size>]
[--cleantime=<clean time>]
[--log=<logfile>]
[--syslog=<facility>]
[--debug=<debuglevel>]
[--pid=<pidfile>]
[--dump=<dumpfile>]
[--quoting | --noquoting]
[--tail | --notail]
[--fromstart | --nofromstart]
[--detach | --nodetach]
[--jointbuf | --nojointbuf]
[--keepopen | --nokeepopen]
[--intevents | --nointevents]
[--intcontexts | --nointcontexts]
[--testonly | --notestonly]
[--help] [-?]
[--version]
DESCRIPTION
SEC is a tool for accomplishing event correlation tasks in the domains of log analysis, system monitoring, network and security management,
etc. Event correlation is a procedure where a stream of events is processed, in order to detect (and act on) certain event groups that
occur within predefined time windows. Unlike many other event correlation products which are heavyweight solutions, SEC is a lightweight
and platform-independent event correlator which runs as a single process.
SEC reads lines from files, named pipes, or standard input, matches the lines with patterns (regular expressions, Perl subroutines, etc.)
for recognizing input events, and correlates events according to the rules in its configuration file(s). Rules are matched against input
in the order they are given in the configuration file. If there are two or more configuration files, rule sequence from every file is
matched against input (unless explicitly specified otherwise). SEC can produce output by executing external programs (e.g., snmptrap(1) or
mail(1)), by writing to files, by calling precompiled Perl subroutines, etc.
Some rules start event correlation operations, while other rules react immediately to input events or system clock. For example, suppose
that SEC has been started with the following command line
/usr/bin/sec --conf=/etc/sec/sshd.rules --input=/var/log/secure
in order to monitor the /var/log/secure syslog file for sshd events. Also, suppose that the /etc/sec/sshd.rules configuration file con-
tains the following rule for correlating SSH failed login syslog events:
type=SingleWithThreshold
ptype=RegExp
pattern=sshd[d+]: Failed .+ for (S+) from [d.]+ port d+ ssh2
desc=Three SSH login failures within 1m for user $1
action=pipe '%s' /bin/mail -s 'SSH login alert' root@localhost
window=60
thresh=3
The pattern field of the rule defines the pattern for recognizing input events, while the ptype field defines its type (regular expres-
sion). Suppose that user risto fails to log in over SSH and the following message is logged to /var/log/secure:
Dec 16 16:24:59 myserver sshd[13685]: Failed password for risto from 10.12.2.5 port 41063 ssh2
This input message will match the regular expression pattern of the above rule, and the match variable $1 will be set to the string risto
(see perlre(1) for details). After a match, SEC will evaluate the operation description string given with the desc field. This is done by
substituting $1 with its current value which yields Three SSH login failures within 1m for user risto. SEC will then check if there
already exists an event correlation operation identified with this string. If the operation is not found, SEC will create a new operation
for the user name risto, and the occurrence time of the input event will be recorded into the operation. Note that for event occurrence
time SEC always uses the current time as returned by the time(2) system call, *not* the timestamp extracted from the event. Suppose that
after 25 seconds, a similar SSH login failure event for the same user name is observed. In this case, a running operation will be found for
the operation description string Three SSH login failures within 1m for user risto, and the occurrence time of the second event is recorded
into the operation. If after 30 seconds a third event for the user name risto is observed, the operation has processed 3 events within 55
seconds. Since the threshold condition "3 events within 60 seconds" (as defined by the thresh and window fields) is now satisfied, SEC will
execute the action defined with the action field -- it will fork a command
/bin/mail -s 'SSH login alert' root@localhost
with a pipe connected to its standard input. Then, SEC writes the operation description string Three SSH login failures within 1m for user
risto (held by the %s special variable) to the standard input of the command through the pipe. In other words, an e-mail warning is sent
to the local root-user. Finally, since there are 5 seconds left until the end of the event correlation window, the operation will consume
the following SSH login failure events for user risto without any further action, and finish after 5 seconds.
The above example illustrates that the desc field of a rule defines the scope of event correlation and influences the number of operations
created by the rule. For example, if we set the desc field to Three SSH login failures within 1m, the root-user would be also alerted on 3
SSH login failure events for *different* users within 1 minute (see EVENT CORRELATION OPERATIONS section for more information).
The following simple example demonstrates that event correlation schemes can be defined by combining several rules. In this example, two
rules harness contexts and synthetic events for achieving their goal:
type=SingleWithThreshold
ptype=RegExp
pattern=sshd[d+]: Failed .+ for (S+) from [d.]+ port d+ ssh2
desc=Three SSH login failures within 1m for user $1
action=event 3_SSH_LOGIN_FAILURES_FOR_$1
window=60
thresh=3
type=EventGroup
init=create USER_COUNTING
end=delete USER_COUNTING
ptype=RegExp
pattern=3_SSH_LOGIN_FAILURES_FOR_(S+)
context=!USER_$1_COUNTED
count=alias USER_COUNTING USER_$1_COUNTED
desc=Repeated SSH login failures for 30 distinct users within 1m
action=pipe '%s' /bin/mail -s 'SSH login alert' root@localhost
window=60
thresh=30
The first rule looks almost identical to the rule from the previous example, but its action field is different -- after three SSH login
failures have been observed for the same user name within one minute by an event correlation operation, the operation will emit the syn-
thetic event 3_SSH_LOGIN_FAILURES_FOR_<username>. Although synthetic events are created by SEC, they are treated like regular events
received from input sources and are matched against rules. The regular expression pattern of the second rule will match the
3_SSH_LOGIN_FAILURES_FOR_<username> event and start a new event correlation operation if no such events have been previously seen. When the
operation is initialized, the context USER_COUNTING is created, and when the operation finishes, this context is deleted (as specified by
the init and end fields). Also, each time a synthetic event for some user name has matched the rule, a context alias for that user name is
created (see the count field). Note that this prevents further matches for the same user name, since a synthetic event for <username> can
match the rule only if the context alias USER_<username>_COUNTED *does not* exist (as requested by the context field; see CONTEXT EXPRES-
SIONS section for more information). The operation started by the rule sends an e-mail warning to the local root-user if 30 synthetic
events have been observed within 1 minute (see the thresh and window fields). Note that due to the use of the USER_<username>_COUNTED
aliases, all synthetic events concern different user names. After sending an e-mail warning, the operation will continue to run until the 1
minute event correlation window expires. When the operation finishes, the deletion of the USER_COUNTING context also erases the USER_<user-
name>_COUNTED aliases.
The above examples have presented the event correlation capabilities of SEC in a very brief fashion. The following sections will provide
an in-depth discussion of SEC features.
OPTIONS
--conf=<file_pattern>
expand <file_pattern> to filenames (with the Perl glob() function) and read event correlation rules from every file. Multiple --conf
options can be specified at command line. Each time SEC receives a signal that forces a configuration reload, <file_pattern> is re-
evaluated. See also INPUT PROCESSING AND TIMING section for a discussion on rule processing order for multiple configuration files.
--input=<file_pattern>[=<context>]
expand <file_pattern> to filenames (with the Perl glob() function) and use the files as input sources. An input file can be a regu-
lar file, named pipe, or standard input if - was specified. Multiple --input options can be specified at command line. Each time SEC
receives the SIGHUP or SIGABRT signal, <file_pattern> is re-evaluated. If SEC experiences a system error when reading from an input
file, it will close the file (use the --reopen-timeout option for reopening the file). If <context> is given, SEC will set up the
context <context> each time it reads a line from input files that correspond to <file_pattern>. This will help the user to write
rules that match data from particular input source(s) only. When there is an --input option with <context> specified, it will auto-
matically enable the --intcontexts option. See INTERNAL EVENTS AND CONTEXTS section for more information.
--input-timeout=<input_timeout>, --timeout-script=<timeout_script>
if SEC has not observed new data in an input file during <input_timeout> seconds (or the file was closed <input_timeout> seconds
ago), <timeout_script> will be executed with command line parameters 1 and <the name of the input file>. If fresh data become avail-
able again, <timeout_script> will be executed with command line parameters 0 and <the name of the input file>. Note that
--input_timeout and --timeout_script options can be used as synonyms for --input-timeout and --timeout-script, respectively.
--reopen-timeout=<reopen_timeout>
if an input file is in the closed state (e.g., SEC fails to open the file at startup, because it has not been created yet), SEC will
attempt to reopen the file after every <reopen_timeout> seconds until open succeeds. Note that --reopen_timeout is a synonym for
--reopen-timeout.
--check-timeout=<check_timeout>
if SEC has not observed new data in an input file, the file will not be polled (both for status and data) during the next
<check_timeout> seconds. Note that --check_timeout is a synonym for --check-timeout.
--poll-timeout=<poll_timeout>
a real number that specifies how many seconds SEC will sleep when no new data were read from input files. Default is 0.1 seconds.
Note that --poll_timeout is a synonym for --poll-timeout.
--blocksize=<io_block_size>
the number of bytes SEC will attempt to read at once from an input file. Default is 1024 (i.e., read from input files by 1KB
blocks).
--bufsize=<input_buffer_size>
set all input buffers to hold last <input_buffer_size> lines. The content of input buffers will be compared with patterns that are
part of rule definitions (i.e., no more than <input_buffer_size> lines can be matched by a pattern at a time). Default buffer size
is 10 lines.
--evstoresize=<event_store_size>
set an upper limit to the number of events in context event stores.
--cleantime=<clean_time>
time interval in seconds that specifies how often internal event correlation and context lists are processed, in order to accomplish
time-related tasks and to remove obsolete elements. See INPUT PROCESSING AND TIMING section for more information. Default is 1 sec-
ond.
--log=<logfile>
use <logfile> for logging SEC activities. Note that if the SEC standard error is connected to a terminal, messages will also be
logged there, in order to facilitate debugging.
--syslog=<facility>
use syslog for logging SEC activities. All messages will be logged with the facility <facility>, e.g., local0 (see syslog(3) for
possible facility values). Warning: be careful with using this option if SEC is employed for monitoring syslog logfiles, because
message loops might occur.
--debug=<debuglevel>
set logging verbosity for SEC. Setting debuglevel to <debuglevel> means that all messages of level <debuglevel> and lower are logged
(e.g., if <debuglevel> is 3, messages from levels 1-3 are logged). The following levels are recognized by SEC:
1 - critical messages (severe faults that cause SEC to terminate, e.g., a failed system call)
2 - error messages (faults that need attention, e.g., an incorrect rule definition in a configuration file)
3 - warning messages (possible faults, e.g., a command forked from SEC terminated with a non-zero exit code)
4 - notification messages (normal system level events and interrupts, e.g., the reception of a signal)
5 - informative messages (information about external programs forked from SEC)
6 - debug messages (detailed information about all SEC activities)
Default <debuglevel> is 6 (i.e., log everything). See SIGNALS section for information on how to change <debuglevel> at runtime.
--pid=<pidfile>
SEC will store its process ID to <pidfile> at startup.
--dump=<dumpfile>
SEC will use <dumpfile> as its dumpfile. See SIGNALS section for more information. Default is /tmp/sec.dump.
--quoting, --noquoting
if the --quoting option is specified, operation description strings that are supplied to command lines of shellcmd and spawn actions
will be put inside apostrophes. All apostrophes ' that strings originally contain will be masked. This option prevents the shell
from interpreting special symbols that operation description strings might contain. Default is --noquoting.
--tail, --notail
if the --notail option is specified, SEC will process all data that are currently available in input files and exit after reaching
all EOFs. Default is --tail -- SEC will jump to the end of input files and wait for new lines to arrive. With the --tail option,
SEC follows an input file both by its name and i-node, and thus handles input file rotations seamlessly. If the input file is
recreated or truncated, SEC will reopen it and process its content from the beginning. If the input file is removed (i.e., there is
just an i-node left without a name), SEC will keep the i-node open and wait for the input file recreation.
--fromstart, --nofromstart
these flags have no meaning when the --notail option is also specified. When used in combination with --tail (or alone, since --tail
is enabled by default), --fromstart will force SEC to read and process input files from the beginning to the end, before the 'tail'
mode is entered. Default is --nofromstart.
--detach, --nodetach
if the --detach option is specified, SEC will disassociate itself from the controlling terminal and become a daemon at startup (note
that SEC will close its standard input, standard output, and standard error, and change its working directory to the root direc-
tory). Default is --nodetach.
--jointbuf, --nojointbuf
if the --jointbuf option is specified, SEC uses joint input buffer for all input sources (the size of the buffer is set with the
--bufsize option). The --nojointbuf option creates a separate input buffer for each input file, and a separate buffer for all syn-
thetic and internal events (the sizes of all buffers are set with the --bufsize option). The --jointbuf option allows multiline pat-
terns to match lines from several input sources, while the --nojointbuf pattern restricts the matching to lines from one input
source only. See INPUT PROCESSING AND TIMING section for more information. Default is --jointbuf.
--keepopen, --nokeepopen
if the --keepopen option is specified, SEC will keep input files open across soft restarts. When the SIGABRT signal is received,
SEC will not reopen input files which have been opened previously, but will only open input files which are in the closed state.
The --nokeepopen option forces SEC to close and (re)open all input files during soft restarts. Default is --nokeepopen.
--intevents, --nointevents
SEC will generate internal events when it starts up, when it receives certain signals, and when it terminates gracefully. Specific
rules can be written to match those internal events, in order to accomplish special tasks at SEC startup, restart, and shutdown.
See INTERNAL EVENTS AND CONTEXTS section for more information. Default is --nointevents.
--intcontexts, --nointcontexts
SEC will create an internal context when it reads a line from an input file. This will help the user to write rules that match data
from particular input source only. See INTERNAL EVENTS AND CONTEXTS section for more information. Default is --nointcontexts.
--testonly, --notestonly
if the --testonly option is specified, SEC will exit immediately after parsing the configuration file(s). If the configuration
file(s) contained no faulty rules, SEC will exit with 0, otherwise with 1. Default is --notestonly.
--help, -?
SEC will output usage information and exit.
--version
SEC will output version information and exit.
Note that options can be introduced both with the single dash (-) and double dash (--), and both the equal sign (=) and whitespace can be
used for separating the option name from the option value. For example, -conf=<file_pattern> and --conf <file_pattern> options are equiva-
lent.
CONFIGURATION FILE
The SEC configuration file consists of rule definitions which are separated by empty and comment lines. Each rule definition consists of
keyword=value fields, one keyword and value per line. Values are case sensitive only where character case is important (like the values
specifying regular expressions). The backslash character () may be used at the end of a line to continue the current rule field in the
next line. Lines which begin with the number sign (#) are treated as comments and ignored (whitespace characters may precede #). Any com-
ment line, empty line, or end of file will terminate the preceding rule definition. For inserting comments into rule definitions, the rem
keyword can be used.
Apart from keywords that are part of rule definitions, label keywords may appear anywhere in the configuration file. The value of each
label keyword will be treated as a label that can be referred to in rule definitions as a point-of-continue. This allows for continuing
event processing at a rule that follows the label, after the current rule has matched and processed the event.
The points-of-continue are defined with continue* fields. Accepted values for these fields are:
TakeNext
after an event has matched the rule, search for matching rules in the configuration file will continue from the next rule.
GoTo <label>
after an event has matched the rule, search for matching rules will continue from the location of <label> in the configuration file
(<label> must be defined with the label keyword anywhere in the configuration file *after* the current rule definition).
DontCont (default value)
after an event has matched the rule, search for matching rules ends in the configuration file.
Before describing each rule type in detail, the following sections discuss patterns, pattern types and match variables, context expres-
sions, and action lists.
PATTERNS, PATTERN TYPES AND MATCH VARIABLES
Patterns and pattern types are defined with pattern* and ptype* fields. Many pattern types define the number of lines N which the pattern
matches (if N is omitted, 1 is assumed). If N is greater than 1, the scope of matching is set with the --jointbuf and --nojointbuf options.
With --jointbuf, the pattern is used for matching N last input lines taken from the joint input buffer (the lines can come from different
input sources). With --nojointbuf, the source of the last input line is identified, and the pattern is matched with N last input lines
from the input buffer of the identified source.
SubStr[N]
pattern is a string that is searched in the last N input lines L1, L2, ..., LN. If N is greater than 1, the input lines are joined
into a string "L1<NEWLINE>L2<NEWLINE>...<NEWLINE>LN", and the pattern string will be searched from it. If the pattern string is
found in input line(s), the pattern matches. Backslash sequences ,
,
, s, and can be used in the pattern for denoting
tabulation, newline, carriage return, space character, and empty string, respectively, while \ denotes backslash itself. For exam-
ple, consider the following pattern definition:
ptype=substr
pattern=Backup done: success
The pattern matches lines containing "Backup done:<TAB>success".
RegExp[N]
pattern is a Perl regular expression (see perlre(1) for more information) for matching the last N input lines L1, L2, ..., LN. If N
is greater than 1, the input lines are joined into a string "L1<NEWLINE>L2<NEWLINE>...<NEWLINE>LN", and the regular expression is
matched with this string. If the regular expression matches, match variables will be set, and these match variables can be used in
other parts of the rule definition.
In addition to numbered match variables ($1, $2, etc.), SEC supports named match variables $+{name} and the $0 variable. The $0
variable holds the entire string of last N input lines that the regular expression has matched. Named match variables can be cre-
ated in newer versions of Perl regular expression language, e.g., (?'myvar'AB|CD) sets $+{myvar} to AB or CD. The special named
match variable $+{_inputsrc} is created by SEC and holds input file name(s) where matching line(s) came from.
Also, SEC allows for match caching and for the creation of additional named match variables through variable maps which are defined
with the varmap* fields. Variable map is a list of name=number mappings separated by semicolons, where name is the name for the
named variable and number identifies a numbered match variable that is set by the regular expression. Each name must begin with a
letter and consist of letters, digits and underscores. After the regular expression has matched, named variables specified by the
map are created from corresponding numbered variables. If the same named variable is set up both from the regular expression and
variable map, the map takes precedence.
If name is not followed by the equal sign and number in the varmap* field, it is regarded as a common name for all match variables
and their values from a successful match. This name is used for caching a successful match by the pattern -- match variables and
their values are stored in the memory-based pattern match cache under name. Cached match results can be reused by Cached and
NCached patterns. Note that before processing each new input line, previous content of the pattern match cache is cleared. Also note
that a successful pattern match is cached even if the subsequent context expression evaluation yields FALSE (see INPUT PROCESSING
AND TIMING section for more information).
For example, consider the following pattern definition:
ptype=regexp
pattern=(?i)(S+.mydomain).*printer: toner/ink low
varmap=printer_toner_or_ink_low; message=0; hostname=1
The pattern matches "printer: toner/ink low" messages in a case insensitive manner from printers belonging to .mydomain. Note that
the printer hostname is assigned to $1 and $+{hostname}, while the whole message line is assigned to $0 and $+{message}. The name of
the file where message line came from is assigned to $+{_inputsrc}. Also, these variables and their values are stored to the pattern
match cache under the name "printer_toner_or_ink_low".
The following pattern definition produces a match if the last two input lines are AAA and BBB:
ptype=regexp2
pattern=^AAA
BBB$
varmap=aaa_bbb
Note that with the --nojointbuf option the pattern only matches if the matching lines are coming from the *same* input file, while
the --jointbuf option lifts that restriction.
In the case of a match, $0 is set to "AAA<NEWLINE>BBB" and $+{_inputsrc} to file name(s) for matching lines. Also, these variable-
value pairs are cached under the name "aaa_bbb".
PerlFunc[N]
pattern is a Perl function for matching the last N input lines L1, L2, ..., LN. The Perl function is compiled at SEC startup with
the Perl eval() function, and eval() must return a code reference for the pattern to be valid (see also PERL INTEGRATION section).
In order to check whether the pattern matches input line(s), SEC will call the function in list context and pass lines L1, L2, ...,
LN and the names of corresponding input files F1, F2, ..., FN to the function as parameters:
function(L1, L2, ..., LN, F1, F2, ..., FN)
Note that with the --nojointbuf option, the function is called with a single file name parameter F, since lines L1, ..., LN are com-
ing from the same input file:
function(L1, L2, ..., LN, F)
Also note that if the input line is a synthetic event, the input file name equals to 'undef'.
If the function returns several values or a single value that is TRUE in boolean context, the pattern matches. If the pattern
matches, return values will be assigned to numbered match variables ($1, $2, etc.). Like with RegExp patterns, the $0 variable is
set to matching input line(s), the $+{_inputsrc} variable is set to input file name(s), and named match variables can be created
from variable maps. For example, consider the following pattern definition:
ptype=perlfunc2
pattern=sub { return ($_[0] cmp $_[1]); }
The pattern compares last two input lines in a stringwise manner ($_[1] holds the last line and $_[0] the preceding one), and
matches if the lines are different. Note that the result of the comparison is assigned to $1, while two matching lines are concate-
nated (with the newline character between them) and assigned to $0. The file name(s) for matching lines are assigned to $+{_input-
src}.
The following pattern definition produces a match if the input line is not a synthetic event and contains either the string "abc" or
"def". The $0 variable is set to the matching line, while $1, $+{file} and $+{_inputsrc} are set to the name of the input file:
ptype=perlfunc
pattern=sub { if (defined($_[1]) && $_[0] =~ /(?:abc|def)/)
{ return $_[1]; } return 0; }
varmap= file=1
Cached pattern is a name that is searched in the pattern match cache (entries are stored into the cache with the varmap* fields). If an
entry with the given name is found in the cache, the pattern matches, and match variables and values are retrieved from the cache.
For example, if the input line matches the following pattern
ptype=perlfunc
pattern=sub { if (defined($_[1]) && $_[0] =~ /(?:abc|def)/)
{ return $_[1]; } return 0; }
varmap=abc_or_def_found; file=1
then the entry "abc_or_def_found" is created in the pattern match cache. Therefore, the pattern
ptype=cached
pattern=abc_or_def_found
will also produce a match for this input line, and set the $0, $1, $+{file}, and $+{_inputsrc} variables to values from the previous
match.
NSubStr[N]
like SubStr[N], except that the result of the match is negated.
NRegExp[N]
like RegExp[N], except that the result of the match is negated and variable maps are not supported. Note that the only match vari-
ables set by the pattern are $0 and $+{_inputsrc}.
NPerlFunc[N]
like PerlFunc[N], except that the result of the match is negated and variable maps are not supported. Note that the only match vari-
ables set by the pattern are $0 and $+{_inputsrc}.
NCached
like Cached, except that the result of the match is negated.
TValue pattern is a truth value, with TRUE and FALSE being legitimate values. TRUE always matches an input line, while FALSE never matches
anything.
When match variables are substituted, each "$$" sequence is interpreted as a literal dollar sign ($) which allows for masking match vari-
ables. For example, the string "Received $$1" becomes "Received $1" after substitution, while "Received $$$1" becomes "Received
$<value_of_1st_var>". In order to disambiguate numbered match variables from the following text, variable number must be enclosed in
braces. For example, the string "Received ${1}0" becomes "Received <value_of_1st_var>0" after substitution, while the string "Received $10"
would become "Received <value_of_10th_var>".
If the match variable was not set by the pattern or was set to 'undef', it is substituted with an empty string (i.e., a zero-width string).
Thus the string "Received $10!" becomes "Received !" after substitution if the pattern did not set $10. (Note that prior to SEC-2.6, unset
or undefined variables were *not* substituted.)
Note that since Pair and PairWithWindow rules have two patterns, match variables of the first pattern are shadowed for some rule fields
when the second pattern matches and sets variables. In order to refer to shadowed variables, their names must begin with % instead of $
(e.g., %1 refers to match variable $1 set by the first pattern). However, the use of the %-prefix is only valid under the following circum-
stances -- *both* pattern types support match variables *and* in the given rule field match variables from *both* patterns can be used.
The %-prefixed match variables are masked with the "%%" sequence (like regular match variables with "$$"). Similarly, the braces can be
used for disambiguating the %-prefixed variables from the following text.
Finally, note that the second pattern of Pair and PairWithWindow rules may contain match variables if the second pattern is of type SubStr,
NSubStr, Regexp, or NRegExp. The variables are substituted at runtime with the values set by the first pattern. If the pattern is a regular
expression, all special characters inside substituted values are masked with the Perl quotemeta() function and the final expression is
checked for correctness.
CONTEXT EXPRESSIONS
Context expressions are boolean expressions that are defined with the context* fields. Context expressions can be used for restricting the
matches produced by patterns, since if the expression evaluates FALSE, the rule will not match an input event.
The context expression accepts context names, Perl miniprograms, and Perl functions as operands. These operands can be combined with the
following operators:
! - logical NOT,
&& - short-circuit logical AND,
|| - short-circuit logical OR.
In addition, parentheses can be used for grouping purposes.
If the operand contains the arrow operator (->), the text following the arrow must be a valid Perl function definition that is compiled at
SEC startup with the Perl eval() function. The eval() must return a code reference (see also PERL INTEGRATION section). information). If
any text precedes the arrow, it is treated as a list of parameters for the function. Parameters must separated by whitespace and may con-
tain match variables set by pattern(s). In order to evaluate the Perl function operand, the function is called in the Perl scalar context.
If the return value of the function is TRUE in the Perl boolean context, the operand evaluates TRUE, otherwise it evaluates FALSE.
If the operand begins with the equal sign (=), the following text must be a Perl miniprogram which is a valid parameter for the Perl eval()
function. The miniprogram may contain match variables set by the pattern(s). In order to evaluate the Perl miniprogram operand, it will be
compiled and executed by calling the Perl eval() function in the Perl scalar context (see also PERL INTEGRATION section). If the return
value from eval() is TRUE in the Perl boolean context, the operand evaluates TRUE, otherwise it evaluates FALSE.
Note that since Perl functions, miniprograms, and parameter lists may contain strings that clash with context expression operators (e.g.,
'!'), it is strongly recommended to enclose them in parentheses, e.g.,
($1 $2) -> (sub { return ($_[0] != $_[1]); })
=({my($temp) = 0; return !$temp;})
If the operand is not a Perl function or miniprogram, it is treated as a context name. As other operands, context names may contain match
variables. If the context name refers to an existing context, the operand evaluates TRUE, otherwise it evaluates FALSE.
If the whole context expression is enclosed in square brackets [], e.g., [MYCONTEXT1 && !MYCONTEXT2], SEC evaluates the expression *before*
pattern matching (normally, the pattern is matched with input line(s) first, so that match variables would be initialized and ready for
expression evaluation). However, if the expression does not contain match variables and many input events are known to match the pattern
but not the expression, the []-operator could save substantial amount of CPU time.
In order to illustrate the discussion, consider the following context expressions:
-> ( sub { my(@stat) = stat("/var/log/messages");
return (!scalar(@stat) || time() - $stat[9] > 3600); } )
($1 $2) -> (sub { return ($_[0] != $_[1]); }) && C1
!(C1 || C2) && =("$1" eq "myhost.mydomain")
The first expression evaluates TRUE if the /var/log/messages file does not exist or was last modified more than 1 hour ago. The second
expression evaluates TRUE if the values of $1 and $2 match variables are numerically unequal and the context C1 exists. The third expres-
sion evaluates TRUE when neither the context C1 nor the context C2 exists and the value of $1 the variable equals to the string
"myhost.mydomain". Note that since && is a short-circuiting operator, the Perl code of the third expression is not evaluated if C1 and/or
C2 exist.
ACTION LISTS
Action lists are defined with the action* fields. An action list consists of action definitions that are separated by semicolons. Each
action definition begins with a keyword specifying the action type. Depending on the action type, parameters may follow, and non-constant
parameters may contain match variables. In order to use semicolons inside a non-constant parameter, the parameter must be enclosed in
parentheses (the outermost set of parentheses will be removed by SEC during configuration file parsing).
Apart from match variables, SEC supports action list variables in action lists which facilitate data sharing between actions and Perl inte-
gration. Each action list variable has a name which must begin with a letter and consist of letters, digits and underscores. In order to
refer to an action list variable, its name must be prefixed by a percent sign (%). Unlike match variables, action list variables can only
be used in action lists and they are substituted with their values immediately before the action list execution. Also, action list vari-
ables continue to exist after the current action list has been executed and can be employed in action lists of other rules.
The following action list variables are predefined by SEC:
%s - operation description string (the value of the desc field after match variables have been substituted with their values). Note that
for the action2 field of Pair and PairWithWindow rules, the %s variable is set by evaluating the desc2 field of the rule.
%t - current time in human-readable format (as returned by the date(1) utility).
%u - current time in seconds since Epoch (as returned by the time(2) system call).
Note that in order to disambiguate the variable from the following text, the variable name must be enclosed in braces (e.g., %{s}). Also,
when action list variables are substituted with their values, each sequence "%%" is interpreted as a literal percent sign (%) which allows
for masking the variables. For example, the string "s%%t" becomes "s%t" after substitution, not "s%<timestamp>".
However, note that if %-prefixed match variables are supported for the action2 field of the Pair or PairWithWindow rule, the sequence "%%%"
must be used in action2 for masking a variable, since the string goes through *two* variable substitution rounds (first for %-prefixed
match variables and then for action list variables, e.g., the string "s%%%t" first becomes "s%%t" and finally "s%t").
Whenever a rule field goes through several substitution rounds, the $ or % characters are masked inside values substituted during earlier
rounds, in order to avoid unwanted side effects during later rounds.
If the action list variable has not been set or its value is 'undef', it is substituted with an empty string (i.e., a zero-width string).
Thus the string "Value of A is: %a" becomes "Value of A is: " after substitution if the variable %a is unset. (Note that prior to SEC-2.6,
unset or undefined variables were *not* substituted.)
Finally, the values are substituted as strings, therefore values of other types (e.g., references) lose their original meaning, unless
explicitly noted otherwise (e.g., if a Perl function reference is stored to an action list variable, the function can later be invoked
through this variable with the call action).
The following actions are supported (optional parameters are enclosed in square brackets):
none No action.
logonly [<string>]
Message <string> is logged to destinations given with the --log and --syslog options. The level of the log message is set to 4 (see
the --debug option for more information on log message levels). Default value for <string> is %s.
write <filename> [<string>]
String <string> with a terminating newline is written to the file <filename> (<filename> may not contain whitespace). File may be a
regular file, named pipe, or standard output (denoted by -). If the file is a regular file, <string> is appended to the end of the
file. If the file does not exist, it is created as a regular file before writing. Default value for <string> is %s.
shellcmd <cmdline>
Fork a process for executing command line <cmdline>. If the --quoting option was specified and <cmdline> contains %s variables, the
value of %s is quoted with apostrophes before substituting it into <cmdline>; note if the value of %s contains apostrophes, they are
masked with backslashes (e.g., abc is converted to 'abc' and aa'bb is converted to 'aa'''bb'). For additional information, see
INTERPROCESS COMMUNICATION section.
spawn <cmdline>
Similar to the shellcmd action, except that each line from the standard output of <cmdline> becomes a synthetic event and will be
treated like a line from input file (see the event action for more information).
pipe '[<string>]' [<cmdline>]
Fork a process for executing command line <cmdline>. The string <string> with a terminating newline is written to the standard input
of <cmdline> (apostrophes are used for disambiguating <string> from <cmdline>). Default value for <string> is %s. If <cmdline> is
omitted, <string> is written to standard output. For additional information, see INTERPROCESS COMMUNICATION section.
create [<name> [<time> [<action list>] ] ]
Create a context with the name <name>, lifetime of <time> seconds, and empty event store. The <name> parameter may not contain
whitespace and defaults to %s. The <time> parameter must evaluate to an unsigned integer at runtime. Specifying 0 for <time> or
omitting the value means infinite lifetime. If <action list> is given, it will be executed when the context expires. If <action
list> contains several actions, the list must be enclosed in parentheses. In <action list>, the internal context name _THIS may be
used for referring to the current context (see INTERNAL EVENTS AND CONTEXTS section for a detailed discussion). If an already
existing context is recreated with create, its remaining lifetime is set to <time> seconds, its action list is reinitialized, and
its event store is emptied.
delete [<name>]
Delete the context <name>. The <name> parameter may not contain whitespace and defaults to %s.
obsolete [<name>]
Similar to the delete action, except that the action list of the context <name> (if present) is executed before deletion.
set <name> <time> [<action list>]
Change settings for the context <name> -- the remaining lifetime of the context is set to <time> seconds, and if the <action list>
parameter is given, the context action list is set to <action list>. The <name> parameter may not contain whitespace and defaults
to %s. The <time> parameter must evaluate to an unsigned integer at runtime. Specifying 0 for <time> or omitting the value means
infinite lifetime. If <action list> contains several actions, the list must be enclosed in parentheses. In <action list>, the
internal context name _THIS may be used for referring to the current context (see INTERNAL EVENTS AND CONTEXTS section for a
detailed discussion).
alias <name> [<alias>]
Create an alias name <alias> for the context <name>. After creation, both <alias> and <name> will point to the same context data
structure, and can thus be used interchangeably for referring to the context. The <name> and <alias> parameters may not contain
whitespace, and <alias> defaults to %s. If the context <name> does not exist, the alias name is not created. If the delete action
is called for one of the context names, the context data structure is destroyed, and all context names (which are now pointers to
unallocated memory) cease to exist. Also note that when the context expires, its action list is executed only once, no matter how
many names the context has.
unalias [<alias>]
Drop an existing context name <alias>, so that it can no longer be used for referring to the given context. The <alias> parameter
may not contain whitespace and defaults to %s. If the name <alias> is the last reference to the context, the unalias action is
identical to delete.
add <name> [<string>]
String <string> is appended to the end of the event store of the context <name>. The <name> parameter may not contain whitespace,
and the <string> parameter defaults to %s. If the context <name> does not exist, the context is created with an infinite lifetime,
empty action list and empty event store (as with create <name>) before adding the string to event store. If <string> is a multi-
line string (i.e., it contains newlines), it is split into lines, and each line is appended to the event store separately.
fill <name> [<string>]
Similar to the add action, except that the event store of the context <name> is emptied before <string> is added.
report <name> [<cmdline>]
Fork a process for executing command line <cmdline>, and write strings from the event store of the context <name> to the standard
input of <cmdline>. Strings are written in the order they appear in the event store, with a terminating newline appended to each
string. If the context <name> does not exist or its event store is empty, <cmdline> is not executed. The <name> parameter may not
contain whitespace, and if <cmdline> is omitted, strings are written to standard output. For additional information, see INTERPRO-
CESS COMMUNICATION section.
copy <name> %<var>
Strings s1,...,sn from the event store of the context <name> are joined into a multi-line string "s1<NEWLINE>...<NEWLINE>sn", and
this string is assigned to the action list variable %<var>. If the context <name> does not exist, the value of %<var> does not
change.
empty <name> [%<var>]
Similar to the copy action, except that the event store of the context <name> will be emptied after the assignment. If %<var> is
omitted, the content of the event store is dropped without an assignment.
event [<time>] [<string>]
After <time> seconds, create a synthetic event <string>. If <string> is a multi-line string (i.e., it contains newlines), it is
split into lines, and from each line a separate synthetic event is created. SEC will treat each synthetic event like a line from an
input file -- the event will be matched against rules and it might trigger further actions. The <time> parameter is an integer con-
stant. Specifying 0 for <time> or omitting the value means "now". Default value for <string> is %s.
tevent <time> [<string>]
Similar to the event action, except that the <time> parameter may contain variables and must evaluate to an unsigned integer at run-
time.
reset [<offset>] [<string>]
Terminate event correlation operation(s) with the operation description string <string>. Note that the reset action works only for
operations started from the same configuration file. The <offset> parameter is used to refer to a specific rule in the configura-
tion file. If <offset> is given, the operation started by the given rule is terminated (if it exists). If <offset> is an unsigned
integer N, it refers to the N-th rule in the configuration file. If <offset> is 0, it refers to the current rule. If <offset> begins
with the plus (+) or minus (-) sign, it specifies an offset from the current rule (e.g., -1 denotes the previous and +1 the next
rule). If <offset> is not given, SEC checks for each rule from the current configuration file if an operation with <string> has
been started by this rule, and the operation is terminated if it exists. Default value for <string> is %s. For additional informa-
tion, see EVENT CORRELATION OPERATIONS section.
getwpos %<var> <offset> [<string>]
Find the beginning of the event correlation window for an event correlation operation, and set the action list variable %<var> to
this timestamp. The value assigned to %<var> is measured in seconds since Epoch (as reported by the time(2) system call). As with
the reset action, the event correlation operation is identified by the operation description string <string> and the rule offset
<offset>. If the operation does not exist, the value of %<var> does not change. Default value for <string> is %s. For additional
information, see EVENT CORRELATION OPERATIONS section.
setwpos <time> <offset> [<string>]
Set the beginning of the event correlation window to <time> for an event correlation operation (if it exists). The <time> parameter
must evaluate to seconds since Epoch (as reported by the time(2) system call), and must reflect a time moment between the previous
window position and the current time (both endpoints included). As with the reset action, the event correlation operation is identi-
fied by the operation description string <string> and the rule offset <offset>. Default value for <string> is %s. For additional
information, see EVENT CORRELATION OPERATIONS section.
assign %<var> [<string>]
Assign string <string> to the action list variable %<var>. Default value for <string> is %s.
eval %<var> <code>
The parameter <code> is a Perl miniprogram that is compiled and executed by calling the Perl eval() function in the Perl list con-
text. If the miniprogram returns a single value, it is assigned to the action list variable %<var>. If the miniprogram returns sev-
eral values s1,...,sn, they are joined into a multi-line string "s1<NEWLINE>...<NEWLINE>sn", and this string is assigned to %<var>.
If no value is returned, %<var> is set to 'undef'. If eval() fails, the value of %<var> does not change. Since most Perl programs
contain semicolons which are also employed by SEC as action separators, it is recommended to enclose the <code> parameter in paren-
theses, in order to mask the semicolons in <code>. For additional information, see PERL INTEGRATION section.
call %<var> %<ref> [<paramlist>]
Call the precompiled Perl function referenced by the action list variable %<ref>, and assign the result to the action list variable
%<var>. The %<ref> parameter must be a code reference that has been previously created with the eval action. The <paramlist> param-
eter (if given) is a string which specifies parameters for the function. The parameters must be separated by whitespace in the
<paramlist> string. If the function returns a single value, it is assigned to %<var>. If the function returns several values
s1,...,sn, they are joined into a multi-line string "s1<NEWLINE>...<NEWLINE>sn", and this string is assigned to %<var>. If no value
is returned, %<var> is set to 'undef'. If the function encounters a fatal runtime error or %<ref> is not a code reference, the
value of %<var> does not change. For additional information, see PERL INTEGRATION section.
lcall %<var> [<paramlist>] -> <code>
Call the precompiled Perl function <code> and assign the result to the action list variable %<var>. The <code> parameter must be a
valid Perl function definition that is compiled at SEC startup with the Perl eval() function, and eval() must return a code refer-
ence. The <paramlist> parameter (if given) is a string which specifies parameters for the function. The parameters must be sepa-
rated by whitespace in the <paramlist> string. If the function returns a single value, it is assigned to %<var>. If the function
returns several values s1,...,sn, they are joined into a multi-line string "s1<NEWLINE>...<NEWLINE>sn", and this string is assigned
to %<var>. If no value is returned, %<var> is set to 'undef'. If the function encounters a fatal runtime error, the value of %<var>
does not change. Since most Perl functions contain semicolons which are also employed by SEC as action separators, it is recom-
mended to enclose the <code> parameter in parentheses, in order to mask the semicolons in <code>. For additional information, see
PERL INTEGRATION section.
rewrite <lnum> [<string>]
Replace last <lnum> lines in the input buffer with string <string>. If the --nojointbuf option was specified and the action is trig-
gered by a matching event, the action modifies the buffer which holds this event. If the --nojointbuf option was specified and the
action is triggered by the system clock (e.g., the action is executed from the Calendar rule), the action modifies the buffer which
holds the last already processed event. With the --jointbuf option, the content of the joint input buffer is rewritten. The <lnum>
parameter must evaluate to an unsigned integer at runtime. If <lnum> evaluates to 0, <lnum> is reset to the number of lines in
<string>. If the value of <lnum> is greater than the buffer size N, <lnum> is reset to N. If <string> contains less than <lnum>
lines, <string> will be padded with leading empty lines. If <string> contains more than <lnum> lines, only leading <lnum> lines from
<string> are written into the buffer. Default value for <string> is %s. For additional information, see INPUT PROCESSING AND TIM-
ING section.
Examples:
spawn /bin/tail -f /var/log/trapd.log
Follow the /var/log/trapd.log file and feed to SEC input all lines that are appended to the file.
pipe '%t: $0' /bin/mail -s "alert message" root@localhost
Mail the timestamp and the value of the $0 variable to the local root.
add ftp_$1 $0; set ftp_$1 1800 (report ftp_$1 /bin/mail root@localhost)
Add the value of the $0 variable to the event store of the context ftp_<the value of $1>. Also extend the context's lifetime for 30 min-
utes, so that when the context expires, its event store will be mailed to the local root.
eval %funcptr ( sub { my(@buf) = split(/
/, $_[0]);
my(@ret) = grep(!/^#/, @buf); return @ret; } );
copy C1 %in; call %out %funcptr %in; fill C1 %out
Create a subroutine for weeding out comment lines from the input list, and use this subroutine for removing comment lines from the event
store of the context C1.
OTHER ISSUES
As already noted, SEC context expressions and action lists may contain parentheses which are used for grouping and masking purposes. When
SEC parses its configuration, it checks whether parentheses in context expressions and action lists are balanced (i.e., whether each paren-
thesis has a counterpart), since unbalanced parentheses introduce ambiguity. This can cause SEC to reject some legitimate constructs, e.g.,
action=eval %o (print ")";)
is considered an invalid action list (however, note that
action=eval %o (print "()";)
would be passed by SEC, since now parentheses are balanced). In order to avoid such parsing errors, each parenthesis without a counterpart
must be masked with a backslash (the backslash will be removed by SEC during configuration file parsing). For example, the above action
could be written as
action=eval %o (print ")";)
SINGLE RULE
The Single rule immediately executes an action list when an event has matched the rule. An event matches the rule if the pattern matches
the event and the context expression (if given) evaluates TRUE.
The Single rule supports the following fields:
type fixed to Single (value is case insensitive, so single or sIngLe can be used instead).
continue (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive).
ptype pattern type (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map.
context (optional)
context expression.
desc operation description string.
action action list.
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in context, desc, and action fields. Also note that this rule does not start an event correlation
operation, and the desc field is merely used for setting the %s action list variable.
Examples:
type=single
continue=takenext
ptype=regexp
pattern=ftpd[(d+)]: S+ (ristov2.*FTP session opened
desc=ftp session opened for ristov2 pid $1
action=create ftp_$1
type=single
continue=takenext
ptype=regexp
pattern=ftpd[(d+)]:
context=ftp_$1
desc=ftp session event for ristov2 pid $1
action=add ftp_$1 $0; set ftp_$1 1800
(report ftp_$1 /bin/mail root@localhost)
type=single
ptype=regexp
pattern=ftpd[(d+)]: S+ (ristov2.*FTP session closed
desc=ftp session closed for ristov2 pid $1
action=report ftp_$1 /bin/mail root@localhost;
delete ftp_$1
This ruleset is created for monitoring the ftpd log file. The first rule creates the context ftp_<pid> when someone connects from host
ristov2 over FTP and establishes a new ftp session (the session is identified by the PID of the process which has been created for handling
this session). The second rule adds all further log file lines for the session <pid> to the event store of the context ftp_<pid> (before
adding a line, the rule checks if the context exists). After adding a line, the rule extends context's lifetime for 30 minutes and sets the
action list that will be executed when the context expires. The third rule mails collected log file lines to root@localhost when the ses-
sion <pid> is closed. Collected lines will also be mailed when the session <pid> has been inactive for 30 minutes (no log file lines
observed for that session).
Note that the log file line that has matched the first rule is also matched against the second rule (since the first rule has the continue
field set to TakeNext). Since the second rule always matches this line, it will become the first line in the event store of ftp_<pid>.
The second rule has also its continue field set to TakeNext, since otherwise no log file lines would reach the third rule.
SINGLEWITHSCRIPT RULE
The SingleWithScript rule forks a process for executing an external program when an event has matched the rule. The names of all currently
existing contexts are written to the standard input of the program. After the program has been forked, the rule matching continues immedi-
ately, and the program status will be checked periodically until the program exits. If the program returns 0 exit status, the action list
defined by the action field is executed; otherwise the action list defined by the action2 field is executed (if given).
The SingleWithScript rule supports the following fields:
type fixed to SingleWithScript (value is case insensitive).
continue (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive).
ptype pattern type (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map.
context (optional)
context expression.
script an external program.
desc operation description string.
action action list.
action2 (optional)
action list.
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in context, script, desc, action, and action2 fields. Also note that this rule does not start an
event correlation operation, and the desc field is merely used for setting the %s action list variable.
Examples:
type=SingleWithScript
ptype=RegExp
pattern=interface ([d.]+) down
script=/bin/ping -c 3 -q $1
desc=Check if $1 responds to ping
action=logonly Interface $1 reported down, but is pingable
action2=pipe '%t: Interface $1 is down' /bin/mail root@localhost
When "interface <ipaddress> down" line appears in input, the rule checks if <ipaddress> responds to ping. If <ipaddress> is pingable, the
message "Interface <ipaddress> reported down, but is pingable" is logged; otherwise an e-mail warning containing a human-readable timestamp
is sent to root@localhost.
SINGLEWITHSUPPRESS RULE
The SingleWithSuppress rule runs event correlation operations for filtering repeated instances of the same event during T seconds. The
value of T is defined by the window field.
When an event has matched the rule, SEC evaluates the operation description string given with the desc field. If the operation for the
given string does not exist, SEC will create it with the lifetime of T seconds, and the operation immediately executes an action list. If
the operation exists, it consumes the matching event without any action.
The SingleWithSuppress rule supports the following fields:
type fixed to SingleWithSuppress (value is case insensitive).
continue (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive).
ptype pattern type (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map.
context (optional)
context expression.
desc operation description string.
action action list.
window event correlation window size (value is an integer constant).
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in context, desc, and action fields.
Examples:
type=SingleWithSuppress
ptype=RegExp
pattern=(S+): [fF]ile system full
desc=File system $1 full
action=pipe '%t: %s' /bin/mail root@localhost
window=900
This rule runs event correlation operations for processing "file system full" syslog messages, e.g.,
Dec 16 14:26:09 test ufs: [ID 845546 kern.notice] NOTICE: alloc: /var: file system full
When the first message for a file system is observed, an operation is created which sends an e-mail warning about this file system to
root@localhost. The operation will then run for 900 seconds and silently consume further messages for the *same* file system. However, if
a message for a different file system is observed, another operation will be started which sends a warning to root@localhost again (since
the desc field contains the $1 match variable which evaluates to the file system name).
PAIR RULE
The Pair rule runs event correlation operations for processing event pairs during T seconds. The value of T is defined by the window field.
Default value is 0 which means infinity.
When an event has matched the conditions defined by the pattern and context field, SEC evaluates the operation description string given
with the desc field. If the operation for the given string exists, it consumes the matching event without any action. If the operation
does not exist, SEC will create it with the lifetime of T seconds, and the operation immediately executes an action list defined by the
action field. SEC will also copy the match conditions given with the pattern2 and context2 field into the operation, and substitute match
variables with their values in copied conditions.
If the event does not match conditions defined by the pattern and context field, SEC will check the match conditions of all operations
started by the given rule. Each matching operation executes the action list given with the action2 field and finishes.
The Pair rule supports the following fields:
type fixed to Pair (value is case insensitive).
continue (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive). Specifies the point-of-continue after a match
by pattern and context.
ptype pattern type for pattern (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map for pattern.
context (optional)
context expression.
desc operation description string.
action action list.
continue2 (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive). Specifies the point-of-continue after a match
by pattern2 and context2.
ptype2 pattern type for pattern2 (value is case insensitive).
pattern2
pattern.
varmap2 (optional)
variable map for pattern2.
context2 (optional)
context expression.
desc2 format string that sets the %s variable for action2.
action2
action list.
window (optional)
event correlation window size (value is an integer constant).
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in context, desc, action, pattern2, context2, desc2, and action2 fields.
Examples:
type=Pair
ptype=RegExp
pattern=kernel: nfs: server (S+) not responding, still trying
desc=Server $1 is not responding
action=pipe '%t: %s' /bin/mail root@localhost
ptype2=SubStr
pattern2=kernel: nfs: server $1 OK
desc2=Server $1 is responding again
action2=logonly
window=3600
This rule runs event correlation operations for processing NFS "server not responding" and "server OK" syslog messages, e.g.,
Dec 18 22:39:48 test kernel: nfs: server box1 not responding, still trying
Dec 18 22:42:27 test kernel: nfs: server box1 OK
When the "server not responding" message for an NFS server is observed, an operation is created for this server which sends an e-mail warn-
ing about the server to root@localhost. The operation will then run for 3600 seconds and silently consume further "server not responding"
messages for the same server. If this operation observes "server OK" message for the *same* server, it will log the message "Server
<servername> is responding again" and finish (because the pattern2 field contains the $1 match variable which evaluates to the server
name).
PAIRWITHWINDOW RULE
The PairWithWindow rule runs event correlation operations for processing event pairs during T seconds. The value of T is defined by the
window field.
When an event has matched the conditions defined by the pattern and context field, SEC evaluates the operation description string given
with the desc field. If the operation for the given string exists, it consumes the matching event without any action. If the operation
does not exist, SEC will create it with the lifetime of T seconds. SEC will also copy the match conditions given with the pattern2 and
context2 field into the operation, and substitute match variables with their values in copied conditions.
If the event does not match conditions defined by the pattern and context field, SEC will check the match conditions of all operations
started by the given rule. Each matching operation executes the action list given with the action2 field and finishes. If the operation
has not observed a matching event by the end of its lifetime, it executes the action list given with the action field before finishing.
The PairWithWindow rule supports the following fields:
type fixed to PairWithWindow (value is case insensitive).
continue (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive). Specifies the point-of-continue after a match
by pattern and context.
ptype pattern type for pattern (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map for pattern.
context (optional)
context expression.
desc operation description string.
action action list.
continue2 (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive). Specifies the point-of-continue after a match
by pattern2 and context2.
ptype2 pattern type for pattern2 (value is case insensitive).
pattern2
pattern.
varmap2 (optional)
variable map for pattern2.
context2 (optional)
context expression.
desc2 format string that sets the %s variable for action2.
action2
action list.
window event correlation window size (value is an integer constant).
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in context, desc, action, pattern2, context2, desc2, and action2 fields.
Examples:
type=PairWithWindow
ptype=RegExp
pattern=sshd[d+]: Failed .+ for (S+) from ([d.]+) port d+ ssh2
desc=User $1 has been unable to log in from $2 over SSH during 1 minute
action=pipe '%t: %s' /bin/mail root@localhost
ptype2=RegExp
pattern2=sshd[d+]: Accepted .+ for $1 from $2 port d+ ssh2
desc2=SSH login successful for %1 from %2 after initial failure
action2=logonly
window=60
This rule runs event correlation operations for processing SSH login events, e.g.,
Dec 27 19:00:24 test sshd[10526]: Failed password for risto from 10.1.2.7 port 52622 ssh2
Dec 27 19:00:27 test sshd[10526]: Accepted password for risto from 10.1.2.7 port 52622 ssh2
When an SSH login failure is observed for a user name and a source IP address, an operation is created for this user name and IP address
combination which expects a successful login for the *same* user name *and* IP address during 60 seconds. For example, when the rule
matches the event
Dec 27 19:00:24 test sshd[10526]: Failed password for risto from 10.1.2.7 port 52622 ssh2
an operation is started which expects an event matching the regular expression
sshd[d+]: Accepted .+ for risto from 10.1.2.7 port d+ ssh2
If the user fails to log in from the same IP address during 60 seconds, the operation sends an e-mail warning to root@localhost before fin-
ishing, otherwise it will log the message "SSH login successful for <username> from <ipaddress> after initial failure" and finish.
SINGLEWITHTHRESHOLD RULE
The SingleWithThreshold rule runs event correlation operations for counting repeated instances of the same event during T seconds, and tak-
ing an action if N events are observed. The values of T and N are defined by the window and thresh field, respectively.
When an event has matched the rule, SEC evaluates the operation description string given with the desc field. If the operation for the
given string does not exist, SEC will create it with the lifetime of T seconds. The operation will memorize the occurrence time of the
event (current time as returned by the time(2) system call), and compare the number of memorized occurrence times with the threshold N. If
the operation has observed N events, it executes the action list defined by the action field, and consumes all further matching events
without any action. If the rule has an optional action list defined with the action2 field, the operation will execute it before finishing.
Note that a sliding window is employed for event counting -- if the operation has observed less than N events by the end of its lifetime,
it drops occurrence times which are older than T seconds, and extends its lifetime for T seconds from the earliest remaining occurrence
time. If there are no remaining occurrence times, the operation finishes without executing an action list.
The SingleWithThreshold rule supports the following fields:
type fixed to SingleWithThreshold (value is case insensitive).
continue (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive).
ptype pattern type (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map.
context (optional)
context expression.
desc operation description string.
action action list.
action2 (optional)
action list.
window event correlation window size (value is an integer constant).
thresh counting threshold (value is an integer constant).
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in context, desc, action, and action2 fields.
Examples:
type=SingleWithThreshold
ptype=RegExp
pattern=sshd[d+]: Failed .+ for (S+) from [d.]+ port d+ ssh2
desc=Three SSH login failures within 1m for user $1
action=pipe '%t: %s' /bin/mail root@localhost
window=60
thresh=3
This rule runs event correlation operations for counting the number of SSH login failure events. Each operation counts events for one user
name, and if the operation has observed three login failures within 60 seconds, it sends an e-mail warning to root@localhost.
If the rule matches five login failure events for different users at the following times:
Dec 28 01:42:21 PM UTC - login failure for risto
Dec 28 01:43:10 PM UTC - login failure for risto
Dec 28 01:43:29 PM UTC - login failure for risto
Dec 28 01:44:00 PM UTC - login failure for risto2
Dec 28 01:44:03 PM UTC - login failure for risto
Dec 28 01:44:07 PM UTC - login failure for risto
then a counting operation is started for the user risto at Dec 28 01:42:21 PM UTC. At Dec 28 01:43:22 PM UTC, the beginning of the event
correlation window is moved to Dec 28 01:43:10 PM UTC for this operation. At Dec 28 01:44:00 PM UTC, a second counting operation is
started for the user risto2. The threshold condition for the first operation will be satisfied at Dec 28 01:44:03 PM UTC (since the opera-
tion has seen three events within 53 seconds) and thus an e-mail warning will be issued. Finally, the event occurring at Dec 28 01:44:07 PM
UTC will be consumed silently by the first operation (the operation will run until Dec 28 01:44:10 PM UTC). If there will be no further
login failure events for the user risto2, the second operation will exist until Dec 28 01:45:00 PM UTC without taking any action.
SINGLEWITH2THRESHOLDS RULE
The SingleWith2Thresholds rule runs event correlation operations which take action if N1 events have been observed in the window of T1 sec-
onds, and then at most N2 events will be observed in the window of T2 seconds. The values of T1, N1, T2, and N2 are defined by the window,
thresh, window2, and thresh2 field, respectively.
When an event has matched the rule, SEC evaluates the operation description string given with the desc field. If the operation for the
given string does not exist, SEC will create it with the lifetime of T1 seconds. The operation will memorize the occurrence time of the
event (current time as returned by the time(2) system call), and compare the number of memorized occurrence times with the threshold N1. If
the operation has observed N1 events, it executes the action list defined by the action field, and starts another counting round for T2
seconds. If no more than N2 events have been observed by the end of the window, the operation executes the action list defined by the
action2 field and finishes. Note that both windows are sliding -- the first window slides like the window of the SingleWithThreshold opera-
tion, while the beginning of the second window is moved to the second earliest memorized event occurrence time when the threshold N2 is
violated.
The SingleWith2Thresholds rule supports the following fields:
type fixed to SingleWith2Thresholds (value is case insensitive).
continue (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive).
ptype pattern type (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map.
context (optional)
context expression.
desc operation description string.
action action list.
window event correlation window size (value is an integer constant).
thresh counting threshold.
desc2 format string that sets the %s variable for action2.
action2
action list.
window2
event correlation window size (value is an integer constant).
thresh2
counting threshold.
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in context, desc, action, desc2, and action2 fields.
Examples:
type=SingleWith2Thresholds
ptype=RegExp
pattern=(S+): %SYS-3-CPUHOG
desc=Router $1 CPU overload
action=pipe '%t: %s' /bin/mail root@localhost
window=300
thresh=2
desc2=Router $1 CPU load has been normal for 1h
action2=logonly
window2=3600
thresh2=0
When a SYS-3-CPUHOG syslog message is received from a router, the rule starts a counting operation for this router which sends an e-mail
warning to root@localhost if another such message is received from the same router within 300 seconds. After sending the warning, the oper-
ation will continue to run until no SYS-3-CPUHOG syslog messages have been received from the router for 3600 seconds. When this condition
is satisfied, the operation will log the message "Router <routername> CPU load has been normal for 1h" and finish.
EVENTGROUP RULE
The EventGroup rule runs event correlation operations for counting repeated instances of N different events e1,...,eK during T seconds, and
taking an action if threshold conditions c1,...,cN for *all* events are satisfied (i.e., for each event eK there are at least cK event
instances in the window). The values for N and T are defined by the type and window field, respectively, while values for c1,...,cN are
given with the thresh* fields. Values for N and c1,...,cN default to 1. Note that the event correlation window is sliding like the window
of the SingleWithThreshold operation.
When an event has matched the rule, SEC evaluates the operation description string given with the desc field. If the operation for the
given string does not exist, SEC will create it with the lifetime of T seconds. The operation will memorize the occurrence time of the
event (current time as returned by the time(2) system call), and compare the number of memorized occurrence times for each eK with the
threshold cK. If all threshold confitions are satisfied, the operation executes the action list defined by the action field, and consumes
all further matching events without re-executing the action list if the multact field is set to No (this is the default). However, if mul-
tact is set to Yes, the operation will evaluate the threshold conditions on every further matching event, executing the action list given
with the action field if all conditions are satisfied, and sliding the event correlation window forward when the window is about to expire
(if no events remain in the window, the operation will finish).
If the rule definition has an optional action list defined with the count* field for event eK, the operation executes it every time an
instance of eK is observed (even if multact is set to No and the operation has already executed the action list given with action).
If the rule definition has an optional action list defined with the init field, the operation executes it immediately after the operation
has been created.
If the rule definition has an optional action list defined with the end field, the operation executes it immediately before the operation
finishes.
If the rule definition has an optional action list defined with the slide field, the operation executes it immediately after the event cor-
relation window has slidden forward. However, note that moving the window with the setwpos action will *not* trigger the execution.
The EventGroup rule supports the following fields:
type EventGroup[N] (value is case insensitive, N defaults to 1).
continue (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive). Specifies the point-of-continue after a match
by pattern and context.
ptype pattern type for pattern (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map for pattern.
context (optional)
context expression.
count (optional)
action list for execution after a match by pattern and context.
thresh (optional)
counting threshold for events matched by pattern and context (value is an integer constant, default is 1).
...
continueN (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive). Specifies the point-of-continue after a match
by patternN and contextN.
ptypeN pattern type for patternN (value is case insensitive).
patternN
pattern.
varmapN (optional)
variable map for patternN.
contextN (optional)
context expression.
countN (optional)
action list for execution after a match by patternN and contextN.
threshN (optional)
counting threshold for events matched by patternN and contextN (value is an integer constant, default is 1).
desc operation description string.
action action list.
init (optional)
action list.
end (optional)
action list.
slide (optional)
action list.
multact (optional)
Yes or No (values are case insensitive, default is No).
window event correlation window size (value is an integer constant).
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in context*, count*, desc, action, init, end, and slide fields.
Examples:
type=EventGroup3
ptype=regexp
pattern=sshd[d+]: Failed .+ for (S+) from ([d.]+) port d+ ssh2
varmap= user=1; ip=2
count=alias OPER_$+{ip} LOGIN_FAILED_$+{user}_$+{ip}
ptype2=regexp
pattern2=sshd[d+]: Accepted .+ for (S+) from ([d.]+) port d+ ssh2
varmap2= user=1; ip=2
context2=LOGIN_FAILED_$+{user}_$+{ip}
ptype3=regexp
pattern3=kernel: iptables:.* SRC=([d.]+)
varmap3= ip=1
desc=Client $+{ip} accessed a firewalled port and had difficulties with logging in
action=pipe '%t: %s' /bin/mail root@localhost
init=create OPER_$+{ip}
slide=delete OPER_$+{ip}; reset 0
end=delete OPER_$+{ip}
window=120
This rule runs event correlation operations for processing iptables and SSH login events, e.g.,
Dec 27 19:00:06 test kernel: iptables: IN=eth0 OUT= MAC=00:13:72:8a:83:d2:00:1b:25:07:e2:1b:08:00 SRC=10.1.2.7 DST=10.2.5.5 LEN=60 TOS=0x00
PREC=0x00 TTL=62 ID=1881 DF PROTO=TCP SPT=34342 DPT=23 WINDOW=5840 RES=0x00 SYN URGP=0
Dec 27 19:00:24 test sshd[10526]: Failed password for risto from 10.1.2.7 port 5 2622 ssh2
Dec 27 19:00:27 test sshd[10526]: Accepted password for risto from 10.1.2.7 port 52622 ssh2
The rule starts an event correlation operation for an IP address if SSH login failure or iptables event was observed for that IP address.
The operation exists for 120 seconds (since when the event correlation window is about to slide, the operation terminates itself with the
reset action as specified with the slide field). The operation sends an e-mail warning to root@localhost if within 120 seconds two condi-
tions hold for the IP address it tracks -- at least one iptables event was observed for the IP *and* and least one login failure for a user
which was followed by a successful login for the same user.
SUPPRESS RULE
The Suppress rule takes no action when an event has matched the rule, and keeps matching events from being processed by later rules in the
configuration file.
The Suppress rule supports the following fields:
type fixed to Suppress (value is case insensitive).
ptype pattern type (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map.
context (optional)
context expression.
desc (optional)
string for describing the rule.
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in the context field. Also note that this rule does not start an event correlation operation, and
the optional desc field is merely used for describing the rule.
Examples:
type=Suppress
ptype=RegExp
pattern=sshd[d+]: Failed .+ for S+ from ([d.]+) port d+ ssh2
context=SUPPRESS_IP_$1
type=SingleWithThreshold
ptype=RegExp
pattern=sshd[d+]: Failed .+ for (S+) from ([d.]+) port d+ ssh2
desc=Three SSH login failures within 1m for user $1 from $2
action=pipe '%t: %s' /bin/mail root@localhost; create SUPPRESS_IP_$2 3600
window=60
thresh=3
The first rule filters out SSH login failure events for an already reported source IP address, so that they will not be matched against the
second rule during 3600 seconds after sending an e-mail warning.
CALENDAR RULE
The Calendar rule was designed for executing actions at specific times. Unlike all other rules, this rule reacts only to the system clock,
ignoring other input. The Calendar rule executes the action list given with the action field if the current time matches all conditions of
the time specification given with the time field. The action list is executed only once for any matching minute.
The rule employs a time specification which closely resembles the crontab(1) style, but there are some subtle differences. The time speci-
fication consists of five or six conditions separated by whitespace. The first condition matches minutes (allowed values are 0-59), the
second condition matches hours (allowed values are 0-23), the third condition days (allowed values are 0-31, with 0 denoting the last day
of the month), the fourth condition months (allowed values are 1-12), and the fifth condition weekdays (allowed values are 0-7, with 0 and
7 denoting Sunday). The sixth condition is optional and matches years (allowed values are 0-99 which denote the last two digits of the
year).
Asterisks (*), ranges of numbers (e.g., 8-11), and lists (e.g., 2,5,7-9) are allowed as conditions. Asterisks and ranges may be augmented
with step values (e.g., 47-55/2 means 47,49,51,53,55).
Note that unlike crontab(1) time specification, the day and weekday conditions are *not* joined with logical OR, but rather with logical
AND. Therefore, 0 1 25-31 10 7 means 1AM on last Sunday in October. On the other hand, with crontab(1) the same specification means 1AM
in every last seven days or every Sunday in October. Also, unlike some versions of cron(8), SEC is not restricted to take action only dur-
ing the first second of the current minute (for example, if SEC is started at the 22th second of a minute, the wildcard condition produces
a match for this minute).
The Calendar rule supports the following fields:
type fixed to Calendar (value is case insensitive).
time time specification.
context (optional)
context expression.
desc operation description string.
action action list.
rem (optional, may appear more than once)
remarks and comments.
Note that this rule does not start event correlation operation, and the desc field is merely used for setting the %s action list variable.
Examples:
type=Calendar
time=0 2 25-31 3,12 6
desc=Check if backup is done on last Saturday of Q1 and Q4
action=event WAITING_FOR_BACKUP
type=Calendar
time=0 2 24-30 6,9 6
desc=Check if backup is done on last Saturday of Q2 and Q3
action=event WAITING_FOR_BACKUP
type=PairWithWindow
ptype=SubStr
pattern=WAITING_FOR_BACKUP
desc=Quarterly backup not completed on time!
action=pipe '%t: %s' /bin/mail root@localhost
ptype2=SubStr
pattern2=BACKUP READY
desc2=Quarterly backup successfully completed
action2=none
window=1800
The first two rules create a synthetic event WAITING_FOR_BACKUP at 2AM on last Saturday of March, June, September and December. The third
rule matches this event and starts an event correlation operation which waits for the BACKUP READY event for 1800 seconds. If this event
has not arrived by 2:30AM, the operation sends an e-mail warning to root@localhost.
JUMP RULE
The Jump rule submits matching events to specific ruleset(s) for further processing. If the event matches the rule, SEC continues the
search for matching rules in configuration file set(s) given with the cfset field. Rules from every file are tried in the order of their
appearance in the file. Configuration file sets can be created from Options rules with the joincfset field, with each set containing at
least one configuration file. If more that one set name is given with cfset, sets are processed from left to right; a matching rule in one
set doesn't prevent SEC from processing the following sets. If the constset field is set to Yes, set names are assumed to be constants and
will not be searched for match variables at runtime.
The Jump rule supports the following fields:
type fixed to Jump (value is case insensitive).
continue (optional)
TakeNext, DontCont or GoTo <label> (apart from <label>, values are case insensitive).
ptype pattern type (value is case insensitive).
pattern
pattern.
varmap (optional)
variable map.
context (optional)
context expression.
cfset (optional)
configuration file set names that are separated by whitespace.
constset (optional)
Yes or No (values are case insensitive, default is Yes).
desc (optional)
string for describing the rule.
rem (optional, may appear more than once)
remarks and comments.
Note that match variables may be used in the context and cfset fields. Also note that this rule does not start event correlation opera-
tions, and the optional desc field is merely used for describing the rule.
Finally, if the cfset field is not present and the continue field is set to GoTo, the Jump rule can be used for skipping rules inside the
current configuration file; if both cfset and continue are not present, Jump is identical to Suppress.
Examples:
type=Jump
ptype=RegExp
pattern=sshd[d+]:
cfset=sshd-rules auth-rules
When an sshd syslog message appears in input, rules from configuration files of the set sshd-rules are first used for matching the message,
and then rules from the configuration file set auth-rules are tried.
OPTIONS RULE
The Options rule sets processing options for the ruleset in the current configuration file. If more than one Options rule is present in the
configuration file, the last instance overrides all previous ones. Note that the Options rule is only processed when SEC (re)starts and
reads in the configuration file. Since this rule is not applied at runtime, it can never match events, react to the system clock, or start
event correlation operations.
The joincfset field lists the names of one or more configuration file sets, and the current configuration file will be added to each set.
If a set doesn't exist, it will be created and the current configuration file becomes its first member. If the procallin field is set to
No, the rules from the configuration file will be used for matching input from Jump rules only.
The Options rule supports the following fields:
type fixed to Options (value is case insensitive).
joincfset (optional)
configuration file set names that are separated by whitespace.
procallin (optional)
Yes or No (values are case insensitive, default is Yes).
rem (optional, may appear more than once)
remarks and comments.
Examples:
The following rule adds the current configuration file to the set sshd-rules which is used for matching input from Jump rules only:
type=Options
joincfset=sshd-rules
procallin=no
The following rule adds the current configuration file to sets linux and solaris which are used for matching all input:
type=Options
joincfset=linux solaris
EVENT CORRELATION OPERATIONS
In order to identify event correlation operations, SEC assigns a key to every operation that is composed from the configuration file name,
the rule ID, and the operation description string (defined by the desc field of the rule). If there are N rules in the configuration file,
the rule IDs belong to the range 0..N-1, and the ID of the k-th rule is k-1. Note that since the configuration file name and rule ID are
part of the key, different rules can start operations with identical description strings without a danger of a clash.
For example, if the configuration file my.conf contains only one rule
type=SingleWithThreshold
ptype=RegExp
pattern=user (S+) login failure on (S+)
desc=Repeated login failures for user $1 on $2
action=pipe '%t: %s' /bin/mail root@localhost
window=60
thresh=3
then the ID of this rule is 0. When this rule matches an input event "user admin login failure on tty1", the desc field yields an opera-
tion description string Repeated login failures for user admin on tty1, and the event will be processed by the operation with the following
key:
my.conf | 0 | Repeated login failures for user admin on tty1
(If the operation for this key does not exist, SEC will start it.) By tuning the desc field of the rule, the scope of individual event
correlation operations can be changed. For instance, the above rule starts three event correlation operations for the following events:
user admin login failure on tty1
user admin login failure on tty5
user admin login failure on tty2
However, if the desc field is set to Repeated login failures for user $1, these events are processed by the *same* event correlation opera-
tion.
Each operation has an event correlation window which defines its scope in time. The size of the window is defined by the window* field, and
the beginning of the window can be obtained with the getwpos action. SingleWithThreshold, SingleWith2Thresholds and EventGroup operations
can slide its window forward during event processing, while for all operations the window can also be moved explicitly with the setwpos
action. Also, with the reset action event correlation operations can be terminated. Note that getwpos, setwpos, and reset actions only work
for operations started by the rules from the same configuration file.
INPUT PROCESSING AND TIMING
SEC processes input data iteratively by reading one line at each iteration, writing this line into a relevant input buffer, and matching
the content of the updated buffer with rules from configuration files.
With the --jointbuf option, SEC employs a joint input buffer for all input sources which holds N last input lines (the value of N can be
set with the --bufsize option). Updating the input buffer means that the new line becomes the first element of the buffer, while the last
element (the oldest line) is removed from the end of the buffer. With the --nojointbuf option, SEC maintains a buffer of N lines for each
input file, and if the input line comes from file F, the buffer of F is updated as described previously. There is also a separate buffer
for synthetic and internal events.
Note that when both synthetic events and regular input are available for reading, synthetic events are always consumed first. When all
synthetic events have been consumed iteratively, SEC will start reading new data from input files.
After the relevant buffer has been updated (every update adds one fresh line and drops one old line), rules from configuration files are
processed, matching the rules against the updated content of the buffer. If during this matching process an action list is executed which
creates new input events (e.g., through the event action), they are *not* written to buffers immediately, but rather consumed at following
iterations.
After each event processing iteration, the pattern match cache is cleared. In other words, if a match is cached with the rule varmap*
field, it is available during ongoing iteration only.
Note that results from a successful pattern matching are also cached when the subsequent context expression evaluation yields FALSE. This
allows for reusing results from partial rule matches. For example, the following rule creates the cache entry "ssh_failed_login" for any
SSH failed login event, even if the context ALERTING_ON does not exist:
type=Single
ptype=RegExp
pattern=sshd[d+]: Failed .+ for (S+) from ([d.]+) port d+ ssh2
varmap=ssh_failed_login; user=1; ip=2
context=ALERTING_ON
desc=SSH login failure for user $1 from $2
action=pipe '%s' /bin/mail -s 'SSH login alert' root@localhost
However, provided the context expression does not contain match variables, enclosing the expression in square brackets (e.g., [ALERT-
ING_ON]) forces its evaluation before the pattern matching, and will thus prevent the matching and the creation of the cache entry if the
evaluation yields FALSE.
Rules from the same configuration file are matched against the buffer content in the order they are given in that file. When multiple con-
figuration files have been specified, rule sequences from all files are matched against the buffer content (unless specified otherwise with
Options rules). The matching order is determined by the order of configuration files in SEC command line. For example, if the Perl glob()
function returns filenames in ascending ASCII order, and configuration files /home/risto/A.conf, /home/risto/B.conf2, and
/home/risto/C.conf are specified with --conf=/home/risto/*.conf --conf=/home/risto/*.conf2 in SEC command line, then SEC first matches the
input against the rule sequence from A.conf, then from C.conf, and finally from B.conf2. Also, note that even if A.conf contains a Sup-
press rule for a particular event, the event is still processed by rulesets in C.conf and B.conf2. However, note that glob() might return
file names in different order if locale settings change. If you want to enforce a fixed order for configuration file application in a por-
table way, it is recommended to create a unique set for each file with the Options rule, and employ the Jump rule for defining the process-
ing order for sets, e.g.:
# This rule appears in A.conf
type=Options
joincfset=FileA
procallin=no
# This rule appears in B.conf2
type=Options
joincfset=FileB
procallin=no
# This rule appears in C.conf
type=Options
joincfset=FileC
procallin=no
# This rule appears in main.conf
type=Jump
ptype=TValue
pattern=TRUE
cfset=FileA FileC FileB
After the relevant input buffer has been updated and its content has been matched by the rules, SEC handles caught signals and checks the
status of child processes. When the timeout specified with the --cleantime option has expired, SEC also checks the status of contexts and
event correlation operations. Therefore, relatively small values should be specified with the --cleantime option, in order to retain the
accuracy of the event correlation process. If the --cleantime option is set to 0, SEC checks event correlation operations and contexts
after processing every input line, but this consumes more CPU time. If the --poll-timeout option value exceeds the value given with
--cleantime, the --poll-timeout option value takes precedence (i.e., sleeps after unsuccessful polls will not be shortened).
Finally, note that apart from the sleeps after unsuccessful polls, SEC measures all time intervals and occurrence times in seconds, and
always uses the time(2) system call for obtaining the current time. Also, for input event occurrence time SEC always uses the time it
observed the event, *not* the timestamp extracted from the event.
INTERNAL EVENTS AND CONTEXTS
In the action list of a context, the context can also be referred with the internal context name _THIS. The name _THIS is created and
deleted dynamically by SEC and it points to the context only during its action list execution. This feature is useful when the context has
had several names during its lifetime (created with the alias action), and it is hard to determine which names exist when the context
expires. For example, if the context is created with create A 60 (report A /bin/mail root) which is immediately followed by alias A B and
unalias A, the report action will fail since the name A no longer refers to the context. However, replacing the first action with create A
60 (report _THIS /bin/mail root) will produce the correct result.
If the --intevents command line option is given, SEC will generate internal events when it is started up, when it receives certain signals,
and when it terminates normally. Inside SEC, internal event is treated as if it was a line that was read from a SEC input file. Specific
rules can be written to match internal events, in order to take some action (e.g., start an external event correlation module with spawn
when SEC starts up). The following internal events are supported:
SEC_STARTUP - generated when SEC is started (this event will always be the first event that SEC sees)
SEC_RESTART - generated after SEC has received the SIGHUP signal and all internal data structures have been cleared (this event will be the
first event that SEC sees after reloading its configuration)
SEC_SOFTRESTART - generated after SEC has received the SIGABRT signal (this event will be the first event that SEC sees after reloading its
configuration)
SEC_SHUTDOWN - generated when SEC receives the SIGTERM signal, or when SEC reaches all EOFs of input files after being started with the
--notail option. After generating SEC_SHUTDOWN event, SEC sleeps for 3 seconds before sending SIGTERM to its child processes (if a child
process was created immediately before SEC_SHUTDOWN, this delay leaves the process enough time for setting the signal handler for SIGTERM).
Before generating an internal event, SEC sets up a context named SEC_INTERNAL_EVENT, in order to disambiguate internal events from regular
input. The SEC_INTERNAL_EVENT context is deleted immediately after the internal event has been matched against all rules.
If the --intcontexts command line option is given, or there is an --input option with a context specified, SEC creates an internal context
each time it reads a line from an input file or a synthetic event. The internal context is deleted immediately after the line has been
matched against all rules. For all input files that have the context name explicitly set with --input=<file_pattern>=<context>, the name of
the internal context is <context>. If the line was read from the input file <filename> for which there is no context name set, the name of
the internal context is _FILE_EVENT_<filename>. For synthetic events, the name of the internal context is _INTERNAL_EVENT. This allows for
writing rules that match data from one particular input source only. E.g., the rule
type=Suppress
ptype=TValue
pattern=TRUE
context=[!_FILE_EVENT_/dev/logpipe]
passes only the lines that were read from /dev/logpipe.
INTERPROCESS COMMUNICATION
The SingleWithScript rule and shellcmd, spawn, pipe, and report actions fork a child process for executing an external program. If the
program command line contains shell metacharacters, the command line is first parsed by the shell which then starts the program. SEC com-
municates with its child processes through pipes (created with the pipe(2) system call). When the child process is at the read end of the
pipe, data have to be written to the pipe in blocking mode which ensures reliable data transmission. In order to avoid being blocked, SEC
forks another child process for writing data to the pipe reliably.
After forking an external program, SEC continues immediately, and checks the program status periodically until the program exits. The run-
ning time of a child process is not limited in any way, and before finishing gracefully, SEC sends the SIGTERM signal to all child pro-
cesses that are still running. If some special exit procedures need to be accomplished in the child process (or the child wishes to ignore
SIGTERM), then the child must install a handler for the SIGTERM signal. Note that if the program command line contains shell metacharac-
ters, the parsing shell will run as a child process of SEC and the parent process of the program. Therefore, the SIGTERM signal will be
sent to the shell, *not* the program. In order to avoid this, the shell's builtin exec command can be used (see sh(1) for more information)
which replaces the shell with the program without forking a new process, e.g.,
action=spawn exec /usr/local/bin/myscript.pl 2>/var/log/myscript.log
Finally, note that if an action list includes two actions which fork external programs, the execution order these programs is not deter-
mined by the order of actions in the list, since both programs are running asynchronously. In order to address this issue, the execution
order must be specified explicitly (e.g., instead of writing action=shellcmd cmd1; shellcmd cmd2, use the shell && operator and write
action=shellcmd cmd1 && cmd2).
PERL INTEGRATION
SEC supports patterns, context expressions, and actions which involve calls to the Perl eval() function. Apart from using action list vari-
ables for data sharing between rules, Perl variables created with eval() can be employed for the same purpose. E.g., when SEC has executed
the following action
action=eval %a ($b = 1)
the variable $b and its value become visible in the following context expression
context= =(++$b > 10)
(with that expression one can implement event counting implicitly). In order to avoid possible clashes with variables inside the SEC code
itself, all calls for eval() are made in the main::SEC namespace (i.e., inside the special package main::SEC). By using the main:: prefix,
SEC data structures can be accessed and modified. For example, the following rules restore and save contexts on SEC startup and shutdown
(SEC keeps all contexts in %main::context_list hash):
type=Single
ptype=SubStr
pattern=SEC_STARTUP
context=SEC_INTERNAL_EVENT
continue=TakeNext
desc=Load the Storable module and terminate if it is not found
action=assign %ret 0; eval %ret (require Storable);
eval %ret (exit(1) unless %ret)
type=Single
ptype=SubStr
pattern=SEC_STARTUP
context=SEC_INTERNAL_EVENT
desc=Restore all SEC contexts from /tmp/SEC_CONTEXTS on startup
action=lcall %ret -> ( sub { %main::context_list =
%{Storable::retrieve("/tmp/SEC_CONTEXTS")}; } )
type=Single
ptype=SubStr
pattern=SEC_SHUTDOWN
context=SEC_INTERNAL_EVENT
desc=Save all SEC contexts into /tmp/SEC_CONTEXTS on shutdown
action=lcall %ret -> ( sub {
Storable::store(\%main::context_list, "/tmp/SEC_CONTEXTS"); } )
However, note that modifying data structures within SEC code is recommended only for advanced users who have carefully studied relevant
parts of the code.
EXAMPLES
This section presents an example rulebase for managing Cisco devices. It is assumed that the managed devices have syslog logging enabled,
and that all syslog messages are sent to a central host and written to logfile(s) that are monitored by SEC.
# Set up contexts NIGHT and WEEKEND for nights
# and weekends. The context NIGHT has a lifetime
# of 8 hours and the context WEEKEND 2 days
type=Calendar
time=0 23 * * *
desc=NIGHT
action=create %s 28800
type=Calendar
time=0 0 * * 6
desc=WEEKEND
action=create %s 172800
# If a router does not come up within 5 minutes
# after it was rebooted, generate event
# "<router> REBOOT FAILURE". The next rule matches
# this event, checks the router with ping and sends
# a notification if there is no response.
type=PairWithWindow
ptype=RegExp
pattern=s([w.-]+) d+: %SYS-5-RELOAD
desc=$1 REBOOT FAILURE
action=event %s
ptype2=RegExp
pattern2=s$1 d+: %SYS-5-RESTART
desc2=%1 successful reboot
action2=logonly
window=300
type=SingleWithScript
ptype=RegExp
pattern=^([w.-]+) REBOOT FAILURE
script=/bin/ping -c 3 -q $1
desc=$1 did not come up after reboot
action=logonly $1 is pingable after reboot
action2=pipe '%t: %s' /bin/mail root@localhost
# Send a notification if CPU load of a router is too
# high (two CPUHOG messages are received within 5
# minutes); send another notification if the load is
# normal again (no CPUHOG messages within last 15
# minutes). Rule is not active at night or weekend.
type=SingleWith2Thresholds
ptype=RegExp
pattern=s([w.-]+) d+: %SYS-3-CPUHOG
context=!(NIGHT || WEEKEND)
desc=$1 CPU overload
action=pipe '%t: %s' /bin/mail root@localhost
window=300
thresh=2
desc2=$1 CPU load normal
action2=pipe '%t: %s' /bin/mail root@localhost
window2=900
thresh2=0
# If a router interface is in down state for less
# than 15 seconds, generate event
# "<router> INTERFACE <interface> SHORT OUTAGE";
# otherwise generate event
# "<router> INTERFACE <interface> DOWN".
type=PairWithWindow
ptype=RegExp
pattern=s([w.-]+) d+: %LINK-3-UPDOWN: Interface ([w.-]+), changed state to down
desc=$1 INTERFACE $2 DOWN
action=event %s
ptype2=RegExp
pattern2=s$1 d+: %LINK-3-UPDOWN: Interface $2, changed state to up
desc2=%1 INTERFACE %2 SHORT OUTAGE
action2=event %s
window=15
# If "<router> INTERFACE <interface> DOWN" event is
# received, send a notification and wait for
# "interface up" event from the same router interface
# for the next 24 hours
type=Pair
ptype=RegExp
pattern=^([w.-]+) INTERFACE ([w.-]+) DOWN
desc=$1 interface $2 is down
action=pipe '%t: %s' /bin/mail root@localhost
ptype2=RegExp
pattern2=s$1 d+: %LINK-3-UPDOWN: Interface $2, changed state to up
desc2=%1 interface %2 is up
action2=pipe '%t: %s' /bin/mail root@localhost
window=86400
# If ten "short outage" events have been observed
# in the window of 6 hours, send a notification
type=SingleWithThreshold
ptype=RegExp
pattern=^([w.-]+) INTERFACE ([w.-]+) SHORT OUTAGE
desc=Interface $2 at node $1 is unstable
action=pipe '%t: %s' /bin/mail root@localhost
window=21600
thresh=10
ENVIRONMENT
If the SECRC environment variable is set, SEC expects it to contain the name of its resource file. Resource file lines which are empty or
which begin with the number sign (#) are ignored (whitespace may precede #). Each remaining line is added to the argv array of SEC as a
*single* element. Also, the lines are added to argv in the order they appear in the resource file. Therefore, if the SEC command line
option has a value, the option name and the value must either be separated by the equal sign (=) or a newline. Here is a simple resource
file example:
# read events from standard input
--input=-
# rules are stored in /etc/sec/test.conf
--conf
/etc/sec/test.conf
Note that although SEC rereads its resource file at the reception of the SIGHUP or SIGABRT signal, adding an option that specifies a cer-
tain startup procedure (e.g., --pid or --detach) will not produce the desired effect at runtime. Also note that the resource file content
is *not* parsed by shell, therefore shell metacharacters are passed to SEC as-is.
SIGNALS
SIGHUP full restart -- SEC will reinterpret its command line and resource file options, reopen its log and input files, reload its configu-
ration, and drop *all* event correlation state (all event correlation operations will be terminated, all contexts will be deleted,
all action list variables will be erased, etc.). SEC will also send the SIGTERM signal to its child processes.
SIGABRT
soft restart -- SEC will reinterpret its command line and resource file options, and reopen its log file. If the --keepopen option
is specified, previously opened input files will remain open across soft restart, otherwise all input files will be reopened. SEC
will (re)load configuration from rule files which have been modified (file modification time returned by stat(2) has changed) or
created after the previous configuration load. SEC will also terminate event correlation operations started from rule files that
have been modified or removed after the previous configuration load. Other operations and previously loaded configuration from
unmodified rule files will remain intact. Note that on some systems SIGIOT is used in place of SIGABRT.
SIGUSR1
detailed information about the current state of SEC (performance and rule matching statistics, running event correlation operations,
created contexts, etc.) will be written to the SEC dumpfile.
SIGUSR2
SEC will reopen its logfile (useful for logfile rotation).
SIGINT SEC will increase its logging level by one; if the current level is 6, the level will be set back to 1. Please note this feature is
available only if SEC standard input is not connected to a terminal (e.g., in daemon mode).
SIGTERM
SEC will terminate gracefully (all SEC child processes will receive SIGTERM).
BUGS
With some locale settings, apostrophes (') in this man page might be displayed incorrectly. As a workaround, set the LANG environment vari-
able to C when reading this man page (e.g., env LANG=C man sec).
AUTHOR
Risto Vaarandi (ristov at users d0t s0urcef0rge d0t net)
SEE ALSO
cron(8), crontab(1), date(1), fork(2), mail(1), perl(1), perlre(1), pipe(2), sh(1), snmptrap(1), stat(2), syslog(3), time(2)
SEC 2.6.2 January 2012 sec(1)