Whoami.EXE Execution Anomaly

Severity: medium
Author: Florian Roth (Nextron Systems)
Source: upstream

Detects the execution of whoami.exe with suspicious parent processes.

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1033` System Owner/User Discovery

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `selection`

or:
Image|endswith: '\whoami.exe'
OriginalFileName: whoami.exe

Stage 2: `not 1 of filter_main_*`

or:
ParentImage|endswith: '\cmd.exe'
ParentImage|endswith: '\powershell.exe'
ParentImage|endswith: '\powershell_ise.exe'
ParentImage|endswith: '\pwsh.exe'
ParentImage: ''
ParentImage: -
ParentImage: null

Stage 3: `not 1 of filter_optional_ms_monitoring_agent`

ParentImage|endswith: ':\Program Files\Microsoft Monitoring Agent\Agent\MonitoringHost.exe'

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
`Image`	ends_with	`\whoami.exe` corpus 18 (sigma 18)
`OriginalFileName`	eq	`whoami.exe` corpus 9 (sigma 9)
`ParentImage`	ends_with	`:\Program Files\Microsoft Monitoring Agent\Agent\MonitoringHost.exe` `\cmd.exe` corpus 13 (sigma 13) `\powershell.exe` corpus 16 (sigma 16) `\powershell_ise.exe` corpus 3 (sigma 3) `\pwsh.exe` corpus 16 (sigma 16)
`ParentImage`	eq	`-` corpus 5 (sigma 5)