Malicious Encoded Payload Decoded and Piped to Shell via xxd or base64 (via process_creation)

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1059.004Unix Shell
Persistence
Priv Esc
Defense Evasion
- T1027Obfuscated Files or Information
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects a hex or base64 encoded blob being decoded with xxd or base64 and piped directly into a shell, the obfuscated execution technique used by the updated XCSSET macOS malware to run its payloads. Adversaries encode commands to hide intent from static inspection and decode-and-run them in memory, so a decode utility feeding sh in one pipeline is a reliable indicator of obfuscated script execution.

Reporting behind it

Related detections9 linkedT1027 — drag to rearrange

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Suspicious Fake GIF Magic Header Written to Disguise Payload File (via process_creation)

Malicious Encoded Payload Decoded and Piped to Shell via xxd or base64 (via process_creation)

Pivot detection · T1027 · 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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