Malicious Payload Assembly via MZ Header Prepend and copy Concatenation (via process_creation)

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 the technique of writing an MZ header and concatenating it with a downloaded blob using copy to reconstruct an executable, used by Bitter APT against PTCL to rebuild the WmRAT payload. The disguised binary is downloaded as a PNG then reassembled on disk. This MZ-prepend and copy pattern is a distinctive evasion behavior.

Reporting behind it

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Malicious Payload Assembly via MZ Header Prepend and copy Concatenation (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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