Run agent control tool to perform a integrity checking immediately (option -a to run on all the agents and -u to specify an agent id)# /var/ossec/bin/agent_control -r -a # /var/ossec/bin/agent_control -r -u <agent_id>
For more information see the agent_control documentation.
Set the option <scan_on_start> to “no” on ossec.conf
Set the file/directory name in the <ignore> option or create a simple local rule.
The following one will ignore files /etc/a and /etc/b and the directory /etc/dir for agents mswin1 and ubuntu-dns:<rule id="100345" level="0" > <if_group>syscheck</if_group> <description>Changes ignored.</description> <match>/etc/a|/etc/b|/etc/dir</match> <hostname>mswin1|ubuntu-dns</hostname> </rule>
No idea. So if there are some directories you do not want scanned at all, make sure they are not included in a
Use the agent_control tool on the manager, to see this information.
More information see the agent_control documentation.
Use the syscheck_control tool on the manager or the web ui for that.
More information see the syscheck_control documentation.
With ossec 1.3 and Fedora you may run into this problem:
You have named files you’d like ossec to monitor so you add:
<ossec_config> <syscheck> <directories check_all="yes">/var/named</directories>
to ossec.conf on the client. Fedora – at least as of version 7 – runs named in a chroot jail under /var/named/chroot. However, part of that chroot jail includes /var/named/chroot/proc. The contents of that directory are purely ephemeral; there is no value to checking their integrity. And, at least in ossec 1.3, your syscheck may stall trying to read those files.
The symptom is a syscheck database on the server that never grows beyond a file or two per restart of the client. The log monitoring continues to work, so you know it’s not a communication issue, and you will often see a slight increase in syscheck database file size after the client has restarted (in one case about 20 minutes after). But the database will never be completely built; there will only be a couple files listed in datebase.
The solution is to add an ignore clause to ossec.conf on the client:
<ossec_config> <syscheck> <ignore>/var/named/chroot/proc</ignore>
By default OSSEC does not alert on new files. To enable this functionlity, <alert_new_files> must be set to yes inside the <syscheck> section of the manager’s ossec.conf. Also, the rule to alert on new files (rule 554) is set to level 0 by default. The alert level will need to be raised in order to see the alert. Alerting on new files does not work in realtime, a full scan will be necessary to detect them.
Add the following to local_rules.xml:
<rule id="554" level="10" overwrite="yes"> <category>ossec</category> <decoded_as>syscheck_new_entry</decoded_as> <description>File added to the system.</description> <group>syscheck,</group> </rule>
<alert_new_files> entry should look something like this:
<syscheck> <frequency>7200</frequency> <alert_new_files>yes</alert_new_files> <directories check_all="yes">/etc,/bin,/sbin</directories> </syscheck>
In short, no. OSSEC does not track this information. You could use your OS’s auditing facilities to track this information, and create a rule to alert when an appropriate log is created.
There is no easy way to do this, but there are work-arounds.
Stop the OSSEC processes on the manager, and run
/var/ossec/bin/syscheck_control -u AGENT_ID.
This will clear the syscheck database for the agent,
and the next time syscheck runs it will create a new baseline.
Next, start the OSSEC processes on the manager.
Once the system update is complete, run a syscheck scan on that agent.
The database will be populated with new values, and should not trigger “file modified” alarms.