Sigma rule: Bad Opsec Defaults Sacrificial Processes With Improper Arguments

Rule

Title

Bad Opsec Defaults Sacrificial Processes With Improper Arguments

Status

test

Level

high

Author

Oleg Kolesnikov @securonix invrep_de, oscd.community, Florian Roth (Nextron Systems), Christian Burkard (Nextron Systems)

Date

2020-10-23

Modified

2024-08-15

File

rules/windows/process_creation/proc_creation_win_susp_bad_opsec_sacrificial_processes.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects attackers using tooling with bad opsec defaults.
E.g. spawning a sacrificial process to inject a capability into the process without taking into account how the process is normally run.
One trivial example of this is using rundll32.exe without arguments as a sacrificial process (default in CS, now highlighted by c2lint), running WerFault without arguments (Kraken - credit am0nsec), and other examples.

Log source

product

windows

category

process_creation

Detection

selection_werfault:
    Image|endswith: '\WerFault.exe'
    CommandLine|endswith: 'WerFault.exe'
selection_rundll32:
    Image|endswith: '\rundll32.exe'
    CommandLine|endswith: 'rundll32.exe'
selection_regsvcs:
    Image|endswith: '\regsvcs.exe'
    CommandLine|endswith: 'regsvcs.exe'
selection_regasm:
    Image|endswith: '\regasm.exe'
    CommandLine|endswith: 'regasm.exe'
selection_regsvr32:
    Image|endswith: '\regsvr32.exe'
    CommandLine|endswith: 'regsvr32.exe'
filter_optional_edge_update:
    ParentImage|contains: '\AppData\Local\Microsoft\EdgeUpdate\Install\{'
    Image|endswith: '\rundll32.exe'
    CommandLine|endswith: 'rundll32.exe'
filter_optional_chromium_installer:
    # As reported in https://github.com/SigmaHQ/sigma/issues/4570 and others
    ParentImage|contains:
        - '\AppData\Local\BraveSoftware\Brave-Browser\Application\'
        - '\AppData\Local\Google\Chrome\Application\'
    ParentImage|endswith: '\Installer\setup.exe'
    ParentCommandLine|contains: '--uninstall '
    Image|endswith: '\rundll32.exe'
    CommandLine|endswith: 'rundll32.exe'
condition: 1 of selection_* and not 1 of filter_optional_*

False positives (as the rule lists them)

• Unlikely

Tags

• attack.stealth
• attack.t1218.011

MITRE ATT&CK ids this rule names

• T1218.011

Related rules

• f5647edc-a7bf-4737-ab50-ef8c60dc3add (obsolete)

References

• https://blog.malwarebytes.com/malwarebytes-news/2020/10/kraken-attack-abuses-wer-service/
• https://www.cobaltstrike.com/help-opsec
• https://twitter.com/CyberRaiju/status/1251492025678983169
• https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/regsvr32
• https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/rundll32
• https://learn.microsoft.com/en-us/dotnet/framework/tools/regasm-exe-assembly-registration-tool
• https://learn.microsoft.com/en-us/dotnet/framework/tools/regsvcs-exe-net-services-installation-tool

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_susp_bad_opsec_sacrificial_processes.yml