PH_Rule_TH_Linux_3
Enabled
Adversaries may attempt to disable the syslog service in an attempt to an attempt to disrupt event logging and evade detection by security controls. This requires process monitoring via FortiSIEM Linux agent.
9
Security
Defense Evasion
Defense Evasion consists of techniques that adversaries use to avoid detection throughout their compromise. Techniques used for defense evasion include uninstalling/disabling security software or obfuscating/encrypting data and scripts. Adversaries also leverage and abuse trusted processes to hide and masquerade their malware. Other tactics’ techniques are cross-listed here when those techniques include the added benefit of subverting defenses.
https://attack.mitre.org/tactics/TA0005T1562.004
Impair Defenses: Disable or Modify System Firewall
Adversaries may disable or modify system firewalls in order to bypass controls limiting network usage. Changes could be disabling the entire mechanism as well as adding, deleting, or modifying particular rules. This can be done numerous ways depending on the operating system, including via command-line, editing Windows Registry keys, and Windows Control Panel. Modifying or disabling a system firewall may enable adversary C2 communications, lateral movement, and/or data exfiltration that would otherwise not be allowed.
https://attack.mitre.org/techniques/T1562/004Server
Linux Process Monitoring via FortiSIEM Agent
Correlation
No remediation guidance specified
If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.
300 seconds
If the following defined pattern/s occur within a 300 second time window.
Filter
This is the named definition of the event query, this is important if multiple subpatterns are defined to distinguish them.
This is the query logic that matches incoming events
eventType = "LINUX_PROCESS_EXEC" AND ((procName = "service" AND swParam CONTAIN "stop") OR (procName = "chkconfig" AND swParam CONTAIN "off") OR (procName = "systemctl" AND swParam REGEXP (".*disable.*|.*stop.*|.*kill.*"))) AND swParam REGEXP (".*syslog.*|.*rsyslog.*|.*syslog-ng.*")
This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID
hostName, user, procName, swParam
This is most typically a numerical constraint that defines when the rule should trigger an incident
COUNT(*) >= 1
This section defines which fields in matching raw events should be mapped to the incident attributes in the resulting incident.
The available raw event attributes to map are limited to the group by attributes and the aggregate event constraint fields for each subpattern
hostName = Filter.hostName,
user = Filter.user,
procName = Filter.procName,
swParam = Filter.swParam