Environment Variable Substring Expansion Obfuscation
Detects command-line obfuscation via Windows environment variable substring expansion (%var:~offset,length%), an evasion technique used by APT37 in the Operation Deepfake/HumanitarianBait-adjacent campaigns to reconstruct malicious commands at runtime and bypass static command-line scanning. This rule catches both the APT37-specific single-character extraction pattern (,1%) and the broader high-count substring-expansion pattern that any obfuscated command exhibits regardless of chunk size. It also flags cmd.exe /k invocation, which APT37 commonly uses.
Cortex XDR
