Suspicious Command Execution via ComSpec Environment Variable Obfuscation

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1059.003Windows Command 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 command lines that reference the delayed-expansion ComSpec variable using the exclamation syntax, an obfuscation Raspberry Robin uses when piping junk-laden files into cmd. Legitimate command lines almost never contain this token, making it a reliable indicator of obfuscated batch execution.

Reporting behind it

Related detections9 linkedT1059.003 — drag to rearrange

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Suspicious File Concatenation via copy Binary Mode

Suspicious Hidden PowerShell Launched by Batch Script

Suspicious Command Shell Executing Batch Script from LNK Delivery

Suspicious PowerShell String Concatenation Obfuscation for Batch Extension via LNK (via process_creation)

Suspicious Office Application Spawning Script Interpreter Chain

Suspicious Command Execution via ComSpec Environment Variable Obfuscation

Pivot detection · T1059.003 · 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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