Suspicious Child Process Of Wermgr.EXE

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

Detects suspicious Windows Error Reporting manager (wermgr.exe) child process

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1055` Process Injection
Defense Evasion	`T1036` Masquerading, `T1055` Process Injection

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation
Security-Auditing	4688	A new process has been created.

Stages and Predicates

Stage 1: `selection`

or:
Image|endswith: '\cmd.exe'
Image|endswith: '\cscript.exe'
Image|endswith: '\ipconfig.exe'
Image|endswith: '\mshta.exe'
Image|endswith: '\net.exe'
Image|endswith: '\net1.exe'
Image|endswith: '\netstat.exe'
Image|endswith: '\nslookup.exe'
Image|endswith: '\powershell.exe'
Image|endswith: '\powershell_ise.exe'
Image|endswith: '\pwsh.exe'
Image|endswith: '\regsvr32.exe'
Image|endswith: '\rundll32.exe'
Image|endswith: '\systeminfo.exe'
Image|endswith: '\whoami.exe'
Image|endswith: '\wscript.exe'
ParentImage|endswith: '\wermgr.exe'

Stage 2: `not 1 of filter_main_rundll32`

or:
CommandLine|contains: -queuereporting
CommandLine|contains: -responsepester
CommandLine|contains: 'C:\Windows\system32\WerConCpl.dll'
CommandLine|contains: 'LaunchErcApp '
Image|endswith: '\rundll32.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
`CommandLine`	match	`-queuereporting` `-responsepester` `C:\Windows\system32\WerConCpl.dll` `LaunchErcApp`
`Image`	ends_with	`\cmd.exe` corpus 92 (sigma 92) `\cscript.exe` corpus 64 (sigma 64) `\ipconfig.exe` corpus 2 (sigma 2) `\mshta.exe` corpus 57 (sigma 57) `\net.exe` corpus 27 (sigma 27) `\net1.exe` corpus 25 (sigma 25) `\netstat.exe` corpus 5 (sigma 5) `\nslookup.exe` corpus 4 (sigma 4) `\powershell.exe` corpus 143 (sigma 143) `\powershell_ise.exe` corpus 27 (sigma 27) `\pwsh.exe` corpus 140 (sigma 140) `\regsvr32.exe` corpus 57 (sigma 57) `\rundll32.exe` corpus 76 (sigma 76) `\systeminfo.exe` corpus 9 (sigma 9) `\whoami.exe` corpus 18 (sigma 18) `\wscript.exe` corpus 64 (sigma 64)
`ParentImage`	ends_with	`\wermgr.exe` corpus 2 (sigma 2)