huntrule

Windows Process Creation: certutil.exe Encodes Files to Base64 in Suspicious Paths

Alert on certutil.exe running with -encode when the command line references files under suspicious directories.

FreeReviewedSigma · High · v2
Product
windows
Category
process_creation
Author
Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2023-05-15
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Defense Evasion

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule identifies executions of certutil.exe using the -encode option to base64-encode a file. It flags activity when the command line indicates the input file resides in paths commonly abused for staging or stealth, such as AppData, Temp, Desktop, PerfLogs, Public, Windows Temp, or the recycle bin. The detection relies on Windows process creation telemetry including the process image/original filename and the full command line.

Reporting behind it

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Windows Process Creation: certutil.exe Encodes Files to Base64 in Suspicious Paths
Pivot detection · T1027 · 9 related

Changelog

v2
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. v1
    No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.