NAME
audisp-prelude - plugin for IDMEF alerts
SYNOPSIS
audisp-prelude [ --test ]
DESCRIPTION
audisp-prelude is a plugin for the audit event dispatcher daemon,
audispd, that uses libprelude to send IDMEF alerts for possible
Intrusion Detection events. This plugin requires connecting to a
prelude-manager to record the events it sends. This plugin will analyze
audit events in realtime and send detected events to the prelude-
manager for correlation, recording, and display.
Events that are currently supported are: Logins, Forbidden Login
Location, Max Concurrent Sessions, Max Login Failures, Forbidden Login
Time, SE Linux AVCs, SE Linux Enforcement Changes, Abnormal Program
Termination, Promiscuous Socket Changes, and watched account logins.
OPTIONS
--test Take input from stdin and write prelude events to stdout but
does not send them to the prelude-manager. This can be used for
debugging or testing the system with suspicious log files when
you do not want it to alert or react.
INSTALLATION
This sensor has to be registered with the prelude-manager before it
will work properly. If the prelude-manager is on the same host as the
sensor, you will need to open two windows to register. If not, you will
have to adjust this example to fit your environment.
In one window, type:
prelude-admin register auditd "idmef:w" localhost --uid 0 --gid 0
In another, type:
prelude-admin registration-server prelude-manager
Follow the on-screen instructions to complete the registration.
TIPS
If you are aggregating multiple machines, you should enable node
information in the audit event stream. You can do this in one of two
places. If you want computer node names written to disk as well as sent
in the realtime event stream, edit the name_format option in
/etc/audit/auditd.conf. If you only want the node names in the realtime
event stream, then edit the name_format option in
/etc/audisp/audispd.conf. Do not enable both as it will put 2 node
fields in the event stream.
At this point, if you want have audit: forbidden login location, max
concurrent sessions, max login failures, and forbidden login time
anomalies being reported, you have to setup pam modules correctly. The
pam modules are respectively: pam_access, pam_limits, pam_tally2, and
pam_time. Please see the respective pam module man pages for any
instructions.
For performance reasons, some audit events will not produce syscall
records which contain additional information about events unless there
is at least one audit rule loaded. If you do not have any additional
audit rules, edit /etc/audit/audit.rules and add something simple that
won’t impact performace like this: -w /etc/shadow -p wa. This rule will
watch the shadow file for writes or changes to its attributes. The
additional audit information provided by having at least one rule will
allow the plugin to give a more complete view of the alert it is
sending.
If you are wanting to get alerts on watched syscalls, watched files,
watched execution, or something becoming executable, you need to add
some keys to your audit rules. For example, if you have the following
audit watch in /etc/audit/audit.rules:
-w /etc/shadow -p wa
and you want idmef alerts on this, you need to add -k ids-file-med or
something appropriate to signal to the plugin that this message is for
it. The format of the key has a fixed format of keywords separated by a
dash. It follows the form of ids-type-severity. The type can be either
sys, file, exec, or mkexe depending on whether you want the event to be
considered a watched_syscall, watched_file, watched_exec, or
watched_mk_exe respectively. The severity can be either info, low, med,
or hi depending on how urgent you would like it to be.
EXAMPLE RULES
To alert on any use of the personality syscall: -a exit,always -S
personality -k ids-sys-med
To alert on a user failing to access the shadow file: -a always,exit -F
path=/etc/shadow -F perms=wa -F success=0 -k ids-file-med
To alert on the execution of a program: -w /bin/ping -p x -k ids-exe-
info
To alert on users making exe’s in their home dir (takes 2 rules): -a
exit,always -S fchmodat -F dir=/home -F a2&0111 -F filetype=file -k
ids-mkexe-hi -a exit,always -S fchmod,chmod -F dir=/home -F a1&0111 -F
filetype=file -k ids-mkexe-hi
FILES
/etc/audisp/plugins.d/au-prelude.conf, /etc/audit/auditd.conf,
/etc/audisp/audispd.conf, /etc/audisp/audisp-prelude.conf
SEE ALSO
audispd(8), prelude-manager(1), auditd.conf(8), audispd.conf(8),
audisp-prelude.conf(5).
AUTHOR
Steve Grubb