Suspicious Certutil Decode of Payload to Executable

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1140Deobfuscate/Decode Files or Information
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects certutil.exe being invoked with a decode flag which APT41 uses to reconstruct an encoded payload such as dns.txt into an executable dns.exe. The living-off-the-land technique evades download-based detection by decoding a locally staged file. It matters because it is a common APT41 first-stage unpacking step.

Reporting behind it

Related detections9 linkedT1140 — drag to rearrange

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Malicious Shell Payload Piped from curl to zsh

CastleLoader ClickFix PowerShell Hex Decode and Re-Execution

Suspicious Cabinet Extraction of Masqueraded vstm Archive via extrac32

Suspicious tar Extraction of Staged Archive to Temp (via process_creation)

Suspicious Certutil Decode of Payload to Executable

Pivot detection · T1140 · 9 related

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

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