Malicious SesameOp Netapi64 Loader DLL Load via Masqueraded Netapi Module (via image_load)

ATT&CK techniques

Defense Evasion → C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1027Obfuscated Files or Information
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1071.001Web Protocols
Exfiltration
Impact

What it detects

This rule detects loading of Netapi64.dll, a loader module used by the SesameOp backdoor that masquerades as a legitimate Windows networking library while relaying commands through the OpenAI Assistants API for command and control. Adversaries use this .NET loader to decrypt and execute payloads under a trusted-looking name, so catching the module load exposes the implant before its covert C2 channel activates.

Reporting behind it

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Malicious SesameOp Netapi64 Loader DLL Load via Masqueraded Netapi Module (via image_load)

Pivot detection · T1071.001 · 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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