Suspicious Base64 Decoding Piped to Shell on macOS

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1059.004Unix Shell
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 base64 decoded output piped directly into a shell interpreter. Microsoft observed XCSSET decoding base64 and OpenSSL-encrypted stages and executing them inline. Piping decoded content straight to sh or bash hides the payload from static inspection, making it a strong obfuscated execution indicator on macOS.

Reporting behind it

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Suspicious Base64 Decoding Piped to Shell on macOS

Pivot detection · T1059.004 · 9 related

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