PH_Rule_Change_29
Enabled
FortiSIEM Windows Agent FIM detected that a file permission changed
7
Change
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/TA0005T1222.001
File and Directory Permissions Modification: Windows File and Directory Permissions Modification
Adversaries may modify file or directory permissions/attributes to evade access control lists (ACLs) and access protected files. Specific file and directory modifications may be a required step for many techniques, such as establishing Persistence via Accessibility Features, Boot or Logon Initialization Scripts, or tainting/hijacking other instrumental binary/configuration files via Hijack Execution Flow.
https://attack.mitre.org/techniques/T1222/001T1565.001
Data Manipulation: Stored Data Manipulation
Adversaries may insert, delete, or manipulate data at rest in order to manipulate external outcomes or hide activity. Stored data could include a variety of file formats, such as Office files, databases, stored emails, and custom file formats. By manipulating stored data, adversaries may attempt to affect a business process, organizational understanding, and decision making.
https://attack.mitre.org/techniques/T1565/001Server
Windows FIM Via FortiSIEM Agent
Correlation
Make sure it is an authorized change
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.
File
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 = "AO-WUA-FileMon-PermissionChange"
This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID
reptDevName,fileName,user,fileOwner
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=File.reptDevName,
fileName=File.fileName,
user=File.user,
fileOwner=File.fileOwner