SesameOp backdoor abuses OpenAI Assistants API
Malware Activity
Summary
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The SesameOp backdoor now uses the OpenAI Assistants API as a covert command-and-control channel, giving operators durable remote access inside compromised environments. It can fetch compressed and encrypted commands, decrypt them, and run them on infected systems, which makes the traffic blend into a legitimate cloud service. The malware was tied to a July 2025 intrusion and is built for long-term espionage rather than short-lived disruption.
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Timeline
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03.11.2025 20:35 2 articles · 6mo ago
Microsoft researchers uncover SesameOp backdoor abusing OpenAI Assistants API
Initial DisclosureMicrosoft security researchers and DART discovered SesameOp during an investigation into a July 2025 cyberattack. The backdoor uses the OpenAI Assistants API as a covert command-and-control channel to fetch compressed and encrypted commands, decrypt and execute them on infected systems, and return harvested information through the same API. Microsoft said the malware does not exploit a vulnerability or misconfiguration in OpenAI's platform, and Microsoft and OpenAI disabled the account and API key used in the attacks while advising defenders to audit firewall logs, enable tamper protection, configure endpoint detection in block mode, and monitor unauthorized external connections.
Show sources
- Microsoft: SesameOp malware abuses OpenAI Assistants API in attacks — www.bleepingcomputer.com — 03.11.2025 20:35
- OpenAI Assistants API Exploited in 'SesameOp' Backdoor — www.infosecurity-magazine.com — 04.11.2025 17:00