PH_Rule_SIGMA_1746
Enabled
Detects the usage of the "Accesschk" utility, an access and privilege audit tool developed by SysInternal and often being abused by attacker to verify process privileges. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_sysinternals_accesschk_check_permissions.yml
5
Security
Discovery
Discovery consists of techniques an adversary may use to gain knowledge about the system and internal network. These techniques help adversaries observe the environment and orient themselves before deciding how to act. They also allow adversaries to explore what they can control and what’s around their entry point in order to discover how it could benefit their current objective. Native operating system tools are often used toward this post-compromise information-gathering objective.
https://attack.mitre.org/tactics/TA0007T1069.001
Permission Groups Discovery: Local Groups
Adversaries may attempt to find local system groups and permission settings via tools such as net localgroup, dscl . -list /Groups, groups. This knowledge can help adversaries determine which groups exist and which users belong to a particular group. Adversaries may use this information to determine which users have elevated permissions, such as the users found within the local administrators group.
https://attack.mitre.org/techniques/T1069/001Server
Windows Sysmon 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="Win-Sysmon-1-Create-Process" AND (product REGEXP "AccessChk$" OR description REGEXP ".*Reports effective permissions.*" OR procName REGEXP "\\accesschk64\.exe$|\\accesschk\.exe$" OR srcFileName="accesschk.exe") AND command REGEXP ".*kwsu .*|.*qwsu .*|.*uwcqv .*|.*uwdqs .*"
This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID
command,description,hostName,procName,product,srcFileName
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
command = Filter.command,
description = Filter.description,
hostName = Filter.hostName,
procName = Filter.procName,
product = Filter.product,
srcFileName = Filter.srcFileName