Potentially Suspicious Child Process Of Regsvr32

Severity: high
Author: elhoim, Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects potentially suspicious child processes of "regsvr32.exe".

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1218.010` System Binary Proxy Execution: Regsvr32

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: '\calc.exe'
Image|endswith: '\cscript.exe'
Image|endswith: '\explorer.exe'
Image|endswith: '\mshta.exe'
Image|endswith: '\net.exe'
Image|endswith: '\net1.exe'
Image|endswith: '\nltest.exe'
Image|endswith: '\notepad.exe'
Image|endswith: '\powershell.exe'
Image|endswith: '\pwsh.exe'
Image|endswith: '\reg.exe'
Image|endswith: '\schtasks.exe'
Image|endswith: '\werfault.exe'
Image|endswith: '\wscript.exe'
ParentImage|endswith: '\regsvr32.exe'

Stage 2: `not 1 of filter_main_werfault`

CommandLine|contains: ' -u -p '
Image|endswith: '\werfault.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	`-u -p` corpus 2 (sigma 2)
`Image`	ends_with	`\calc.exe` corpus 13 (sigma 13) `\cscript.exe` corpus 64 (sigma 64) `\explorer.exe` corpus 12 (sigma 12) `\mshta.exe` corpus 57 (sigma 57) `\net.exe` corpus 27 (sigma 27) `\net1.exe` corpus 25 (sigma 25) `\nltest.exe` corpus 9 (sigma 9) `\notepad.exe` corpus 11 (sigma 11) `\powershell.exe` corpus 143 (sigma 143) `\pwsh.exe` corpus 140 (sigma 140) `\reg.exe` corpus 46 (sigma 46) `\schtasks.exe` corpus 45 (sigma 45) `\werfault.exe` corpus 4 (sigma 4) `\wscript.exe` corpus 64 (sigma 64)
`ParentImage`	ends_with	`\regsvr32.exe` corpus 11 (sigma 11)