Wazuh rule

The custom rule would look as follows:

  <rule id="100002" level="10">
    <if_group>sysmon_event1</if_group>
    <field name="win.eventdata.originalFileName" type="pcre2">(?i)mimikatz\.exe</field>
    <description>Mimikatz usage detected.</description>
    <mitre>
      <id>T1003</id>
    </mitre>
  </rule>    

1. <rule id="100002" level="10">: This is the rule definition with an ID of 100002 and a severity level of 10.

2. <if_group>sysmon_event1</if_group>: This specifies the condition or event group that triggers the rule. In this case, it's "sysmon_event1."

3. <field name="win.eventdata.originalFileName" type="pcre2">(?i)mimikatz\.exe</field>: This part defines a condition on a specific field in the event data. It checks if the original file name in the Windows event data matches the regular expression "(?i)mimikatz.exe" case-insensitively.

   • name="win.eventdata.originalFileName": Specifies the field to check.

   • type="pcre2": Indicates the type of regular expression used.

   • (?i)mimikatz\.exe: The actual regular expression to match against the original file name.

4. <description>Mimikatz usage detected.</description>: Provides a human-readable description of what the rule is checking for. In this case, it states that the rule is detecting the usage of Mimikatz.

5. <mitre><id>T1003</id></mitre>: Associates the rule with a specific MITRE ATT&CK technique ID. In this case, it's T1003, which is "Credential Dumping."

Adding rules

We can follow either of the following methods to add custom rules:

• GUI method

• CLI method