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

Related detections9 linkedT1059.003 — drag to rearrange

Suspicious Command Execution via ComSpec Environment Variable Obfuscation

Suspicious PIF Payload Assembly via copy /b Binary Concatenation

Obfuscated Encoded PowerShell Payload Deployed via Process Execution (via process_creation)

Malicious KB Document Masqueraded Executable Spawned by Script Interpreter via RoKRAT Loader (via process_creation)

Suspicious Archive Extraction From AppData Staging Folder via Process Creation

Suspicious Scheduled Task Creation Referencing dllFake Batch Scripts (via process_creation)

Suspicious Encoded PowerShell Using Base64 Stream Decompression Routines (via process_creation)

Suspicious Backup Exec Remote Agent Spawning Command Shell via Process Creation (via process_creation)

Suspicious ClickFix Command Execution via RunMRU Registry Key

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

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.

Full detection rule

Unlock this rule to view and copy it

The detection logic is included with a plan. Everything else — context, mappings and implementation details — stays free on this page.

Sign in for 3 free unlocks

Signing in gives you 3 unlocks to spend on any rule in the library. No card, and they do not expire.

Also included

Unlocked rules convert on this page — to Splunk SPL or Splunk — Raw Index SPL or Microsoft Sentinel KQL or Microsoft Sentinel ASIM ASIM KQL or Microsoft Defender XDR KQL or Elastic Security KQL or Elastic Security Lucene or Elastic Security ES|QL or CrowdStrike Falcon CQL or SentinelOne PowerQuery or Palo Alto Cortex XDR XQL or Carbon Black Cloud Platform Search or Carbon Black EDR Process Search or Google Security Operations UDM Search or IBM QRadar AQL or Sumo Logic Cloud SIEM Rules expression or Rapid7 InsightIDR LEQL or Graylog Search or OpenSearch Lucene or OpenSearch PPL PPL or Grafana Loki LogQL or SQLite SQL or Zircolite SQLite — with the log-source profile the engine picked, the field map it used, and everything it could not express. Converting a rule you have unlocked costs no further credit.

See it run on a free rule →Convert your own rule →