Abused Debug Privilege by Arbitrary Parent Processes

Severity: high
Author: Semanur Guneysu @semanurtg, oscd.community
Source: upstream

Detection of unusual child processes by different system processes

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1548` Abuse Elevation Control Mechanism
Defense Evasion	`T1548` Abuse Elevation Control Mechanism

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_parent`

or:
ParentImage|endswith: '\csrss.exe'
ParentImage|endswith: '\lsass.exe'
ParentImage|endswith: '\searchindexer.exe'
ParentImage|endswith: '\services.exe'
ParentImage|endswith: '\smss.exe'
ParentImage|endswith: '\spoolsv.exe'
ParentImage|endswith: '\wininit.exe'
ParentImage|endswith: '\winlogon.exe'
or:
User|contains: AUTHORI
User|contains: AUTORI

Stage 2: `all of selection_img`

or:
Image|endswith: '\cmd.exe'
Image|endswith: '\powershell.exe'
Image|endswith: '\pwsh.exe'
OriginalFileName: Cmd.Exe
OriginalFileName: PowerShell.EXE
OriginalFileName: pwsh.dll

Stage 3: `not filter`

CommandLine|contains: ' ADD '
CommandLine|contains: ' route '

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	`ADD` `route`
`Image`	ends_with	`\cmd.exe` corpus 92 (sigma 92) `\powershell.exe` corpus 143 (sigma 143) `\pwsh.exe` corpus 140 (sigma 140)
`OriginalFileName`	eq	`Cmd.Exe` corpus 32 (sigma 30, splunk 2) `PowerShell.EXE` corpus 64 (sigma 60, splunk 4) `pwsh.dll` corpus 72 (sigma 68, splunk 4)
`ParentImage`	ends_with	`\csrss.exe` corpus 3 (sigma 3) `\lsass.exe` corpus 3 (sigma 3) `\searchindexer.exe` `\services.exe` corpus 7 (sigma 7) `\smss.exe` corpus 3 (sigma 3) `\spoolsv.exe` corpus 4 (sigma 4) `\wininit.exe` corpus 2 (sigma 2) `\winlogon.exe` corpus 3 (sigma 3)
`User`	match	`AUTHORI` corpus 16 (sigma 16) `AUTORI` corpus 16 (sigma 16)