Suspicious PowerShell Parent Process

Severity: high
Author: Teymur Kheirkhabarov, Harish Segar
Source: upstream

Detects a suspicious or uncommon parent processes of PowerShell

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1059.001` Command and Scripting Interpreter: PowerShell

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_parent`

or:
ParentImage|endswith: '\MicrosoftEdgeSH.exe'
ParentImage|endswith: '\amigo.exe'
ParentImage|endswith: '\browser.exe'
ParentImage|endswith: '\chrome.exe'
ParentImage|endswith: '\firefox.exe'
ParentImage|endswith: '\httpd.exe'
ParentImage|endswith: '\iexplore.exe'
ParentImage|endswith: '\jbosssvc.exe'
ParentImage|endswith: '\microsoftedge.exe'
ParentImage|endswith: '\microsoftedgecp.exe'
ParentImage|endswith: '\mshta.exe'
ParentImage|endswith: '\nginx.exe'
ParentImage|endswith: '\outlook.exe'
ParentImage|endswith: '\php-cgi.exe'
ParentImage|endswith: '\regsvr32.exe'
ParentImage|endswith: '\rundll32.exe'
ParentImage|endswith: '\safari.exe'
ParentImage|endswith: '\services.exe'
ParentImage|endswith: '\sqlagent.exe'
ParentImage|endswith: '\sqlserver.exe'
ParentImage|endswith: '\sqlservr.exe'
ParentImage|endswith: '\vivaldi.exe'
ParentImage|endswith: '\w3wp.exe'
ParentImage|contains: tomcat

Stage 2: `all of selection_powershell`

or:
CommandLine|contains: '/c powershell'
CommandLine|contains: '/c pwsh'
Description: 'Windows PowerShell'
Image|endswith: '\powershell.exe'
Image|endswith: '\pwsh.exe'
OriginalFileName: PowerShell.EXE
OriginalFileName: pwsh.dll
Product: 'PowerShell Core 6'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`CommandLine`	match	`/c powershell` `/c pwsh`
`Description`	eq	`Windows PowerShell` corpus 2 (sigma 2)
`Image`	ends_with	`\powershell.exe` corpus 143 (sigma 143) `\pwsh.exe` corpus 140 (sigma 140)
`OriginalFileName`	eq	`PowerShell.EXE` corpus 64 (sigma 60, splunk 4) `pwsh.dll` corpus 72 (sigma 68, splunk 4)
`ParentImage`	ends_with	`\MicrosoftEdgeSH.exe` `\amigo.exe` `\browser.exe` `\chrome.exe` corpus 4 (sigma 4) `\firefox.exe` corpus 3 (sigma 3) `\httpd.exe` corpus 6 (sigma 6) `\iexplore.exe` corpus 2 (sigma 2) `\jbosssvc.exe` `\microsoftedge.exe` corpus 2 (sigma 2) `\microsoftedgecp.exe` `\mshta.exe` corpus 10 (sigma 10) `\nginx.exe` corpus 6 (sigma 6) `\outlook.exe` corpus 4 (sigma 4) `\php-cgi.exe` corpus 6 (sigma 6) `\regsvr32.exe` corpus 11 (sigma 11) `\rundll32.exe` corpus 12 (sigma 12) `\safari.exe` `\services.exe` corpus 7 (sigma 7) `\sqlagent.exe` corpus 2 (sigma 2) `\sqlserver.exe` `\sqlservr.exe` corpus 3 (sigma 3) `\vivaldi.exe` corpus 2 (sigma 2) `\w3wp.exe` corpus 8 (sigma 8)
`ParentImage`	match	`tomcat`
`Product`	eq	`PowerShell Core 6` corpus 2 (sigma 2)