Sigma rule: Qakbot Rundll32 Fake DLL Extension Execution

Rule

Title

Qakbot Rundll32 Fake DLL Extension Execution

Status

test

Level

critical

Author

X__Junior (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)

Date

2023-05-24

File

rules-emerging-threats/2023/Malware/Qakbot/proc_creation_win_malware_qakbot_rundll32_fake_dll_execution.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects specific process tree behavior of a "rundll32" execution where the DLL doesn't have the ".dll" extension. This is often linked with potential Qakbot activity.

Log source

product

windows

category

process_creation

Detection

selection:
    ParentImage|endswith:
        # Note: Only add processes seen used by Qakbot to avoid collision with other strains of malware
        - '\cmd.exe'
        - '\cscript.exe'
        - '\curl.exe'
        - '\mshta.exe'
        - '\powershell.exe'
        - '\pwsh.exe'
        - '\wscript.exe'
    Image|endswith: '\rundll32.exe'
    CommandLine|contains:
        # Note: Only add paths seen used by Qakbot to avoid collision with other strains of malware
        - ':\ProgramData\'
        - ':\Users\Public\'
        - '\AppData\Local\Temp\'
        - '\AppData\Roaming\'
filter_main_extension:
    CommandLine|contains: '.dll'
condition: selection and not 1 of filter_main_*

False positives (as the rule lists them)

• Unlikely

Tags

• attack.execution
• detection.emerging-threats
• attack.stealth

References

• https://github.com/pr0xylife/Qakbot/

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2023/Malware/Qakbot/proc_creation_win_malware_qakbot_rundll32_fake_dll_execution.yml