How it works

Log files

The Log analysis engine can be configured to monitor specific files on the servers.

• Linux:

  <localfile>
    <location>/var/log/example.log</location>
    <log_format>syslog</log_format>
  </localfile>
  

• Windows:

  <localfile>
    <location>C:\myapp\example.log</location>
    <log_format>syslog</log_format>
  </localfile>
  

Windows event logs

Wazuh can monitor classic Windows event logs, as well as the newer Windows event channels.

• Event log:

  <localfile>
    <location>Security</location>
    <log_format>eventlog</log_format>
  </localfile>
  

• Event channel:

  <localfile>
    <location>Microsoft-Windows-PrintService/Operational</location>
    <log_format>eventchannel</log_format>
  </localfile>
  

Remote syslog

In order to integrate network devices such as routers, firewalls, etc, the log analysis component can be configured to receive log events through syslog. To do that we have two methods available:

One option is for Wazuh to receive syslog logs by a custom port:

<ossec_config>
  <remote>
    <connection>syslog</connection>
    <port>513</port>
    <protocol>udp</protocol>
    <allowed-ips>192.168.2.0/24</allowed-ips>
  </remote>
<ossec_config>

• <connection>syslog</connection> indicates that the manager will accept incoming syslog messages from across the network.

• <port>513</port> defines the port that Wazuh will listen to retrieve the logs. The port must be free.

• <protocol>udp</protocol> defines the protocol to listen the port. It can be UDP or TCP.

• <allowed-ips>192.168.2.0/24</allowed-ips> defines the network or IP from which syslog messages will be accepted.

The other option store the logs in a plaintext file and monitor that file with Wazuh. If a /etc/rsyslog.conf configuration file is being used and we have defined where to store the syslog logs we can monitor them in Wazuh ossec.conf using a <localfile> block with syslog as the log format.

<localfile>
  <log_format>syslog</log_format>
  <location>/custom/file/path</location>
</localfile>

• <log_format>syslog</log_format> indicates the source log format, in this case, syslog format.

• <location>/custom/file/path</location> indicates where we have stored the syslog logs.

Pre-decoding

In the pre-decoding phase of analysis, static information from well-known fields all that is extracted from the log header.

Feb 14 12:19:04 localhost sshd[25474]: Accepted password for rromero from 192.168.1.133 port 49765 ssh2

Extracted information:

• hostname: 'localhost'

• program_name: 'sshd'

Decoding

In the decoding phase, the log message is evaluated to identify what type of log it is and known fields for that specific log type are then extracted.

Sample log and its extracted info:

Feb 14 12:19:04 localhost sshd[25474]: Accepted password for rromero from 192.168.1.133 port 49765 ssh2

Extracted information:

• program name: sshd

• dstuser: rromero

• srcip: 192.168.1.133

Rule matching

In the next phase, the extracted log information is compared to the ruleset to look for matches:

For the previous example, rule 5715 is matched:

<rule id="5715" level="3">
  <if_sid>5700</if_sid>
  <match>^Accepted|authenticated.$</match>
  <description>sshd: authentication success.</description>
  <group>authentication_success,pci_dss_10.2.5,</group>
</rule>