PH_Rule_SIGMA_1742
Enabled
Detects adding and using Exchange PowerShell snap-ins to export mailbox data. As seen used by HAFNIUM and APT27. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_snapins_hafnium.yml
7
Security
Execution
Execution consists of techniques that result in adversary-controlled code running on a local or remote system. Techniques that run malicious code are often paired with techniques from all other tactics to achieve broader goals, like exploring a network or stealing data. For example, an adversary might use a remote access tool to run a PowerShell script that does Remote System Discovery.
https://attack.mitre.org/tactics/TA0002T1059.001
Command and Scripting Interpreter: PowerShell
Adversaries may abuse PowerShell commands and scripts for execution. Adversaries can use PowerShell to perform a number of actions, including discovery of information and execution of code.
https://attack.mitre.org/techniques/T1059/001Server
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 ((procName REGEXP "\\powershell\.exe$|\\pwsh\.exe$" OR srcFileName IN ("PowerShell.EXE","pwsh.dll")) AND command REGEXP ".*Add-PSSnapin.*" AND command REGEXP ".*Microsoft\.Exchange\.Management\.PowerShell\.SnapIn.*|.*Microsoft\.Exchange\.Powershell\.Snapin.*") AND ((parentProcName!="C:\\Windows\\System32\\msiexec.exe" OR command NOT REGEXP ".*\$exserver=Get-ExchangeServer \(\[Environment\]::MachineName\) -ErrorVariable exerr 2> \$null.*"))
This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID
command,hostName,parentProcName,procName,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,
hostName = Filter.hostName,
parentProcName = Filter.parentProcName,
procName = Filter.procName,
srcFileName = Filter.srcFileName