Sigma rule: CVE-2021-31979 CVE-2021-33771 Exploits by Sourgum

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-c8bb7e1b82c6, updated 2022-10-09T00:00:00.000Z.

Rule

Title
CVE-2021-31979 CVE-2021-33771 Exploits by Sourgum
Status
test
Level
critical
Author
Sittikorn S
Date
2021-07-16
Modified
2022-10-09
File
rules-emerging-threats/2021/Exploits/CVE-2021-33771/file_event_win_cve_2021_31979_cve_2021_33771_exploits.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects patterns as noticed in exploitation of Windows CVE-2021-31979 CVE-2021-33771 vulnerability and DevilsTongue malware by threat group Sourgum

Log source

product
windows
category
file_event

Detection

selection:
    TargetFilename|contains:
        - 'C:\Windows\system32\physmem.sys'
        - 'C:\Windows\System32\IME\IMEJP\imjpueact.dll'
        - 'C:\Windows\system32\ime\IMETC\IMTCPROT.DLL'
        - 'C:\Windows\system32\ime\SHARED\imecpmeid.dll'
        - 'C:\Windows\system32\config\spp\ServiceState\Recovery\pac.dat'
        - 'C:\Windows\system32\config\cy-GB\Setup\SKB\InputMethod\TupTask.dat'
        - 'C:\Windows\system32\config\config\startwus.dat'
        - 'C:\Windows\system32\ime\SHARED\WimBootConfigurations.ini'
        - 'C:\Windows\system32\ime\IMEJP\WimBootConfigurations.ini'
        - 'C:\Windows\system32\ime\IMETC\WimBootConfigurations.ini'
condition: selection

False positives (as the rule lists them)

  • Unlikely

Tags

  • attack.initial-access
  • attack.execution
  • attack.credential-access
  • attack.t1566
  • attack.t1203
  • cve.2021-33771
  • cve.2021-31979
  • detection.emerging-threats

CVEs this rule names

MITRE ATT&CK ids this rule names

References

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/2021/Exploits/CVE-2021-33771/file_event_win_cve_2021_31979_cve_2021_33771_exploits.yml

Sources and licences

  • SigmaHQ

    "CVE-2021-31979 CVE-2021-33771 Exploits by Sourgum" by Sittikorn S (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2021/Exploits/CVE-2021-33771/file_event_win_cve_2021_31979_cve_2021_33771_exploits.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: CVE-2021-31979 CVE-2021-33771 Exploits by Sourgum",
entity page, dataset version ref-c8bb7e1b82c6, updated 2022-10-09T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/ad7085ac-92e4-4b76-8ce2-276d2c0e68ef (accessed 2026-11-03).
Underlying source: SigmaHQ rule ad7085ac-92e4-4b76-8ce2-276d2c0e68ef, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.