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SesameOp: Novel backdoor uses OpenAI Assistants API for command and control - AI Case Study

The Microsoft Incident Response - Detection and Response Team (DART) investigated a compromised system where a threat actor utilized SesameOp, a backdoor implant that abuses the OpenAI Assistants API as a covert command and control channel, for espionage activities. The SesameOp malware used the OpenAI API to fetch and execute the threat actor’s commands and to exfiltrate encrypted results from the victim system...

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IncidentOpenAI Assistants APIUnknown Threat ActorCommand and Control

Overview

Case steps1Steps described in the case record.
Techniques1Attack methods mentioned in the case steps.
Linked CVEs0Known vulnerabilities mentioned in the record.

Risk patterns

Patterns found in the case record and its linked vulnerabilities.

  • 1Dominant ATLAS tactic. Command and Control appears in 1 case steps.

Procedure timeline

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Command and Control1
  1. Command and Control

    The threat actor abused the OpenAI Assistants API to relay commands to the SesameOp malware, which executed them on the victim system, and sent the results back to the threat actor via the same channel. Both commands and results are encrypted. SesameOp cleaned up its tracks by deleting the Assistants and Messages it created and used for communication.

Related CVEs

Known software flaws mentioned in the case record.

No related CVEs found for this case. Built from MITRE ATLAS case study records and listed case steps.

Mitigations

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No connected defenses found for this case. Built from the attack methods identified in the case record.

Sources

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Original source

Original source links

Open the MITRE ATLAS data and public references used for this case study.

Repositoryhttps://github.com/mitre-atlas/atlas-dataATLAS.yamlhttps://github.com/mitre-atlas/atlas-data/blob/main/dist/ATLAS.yamlSchemahttps://github.com/mitre-atlas/atlas-data/blob/main/dist/schemas/atlas_output_schema.jsonSesameOp: Novel backdoor uses OpenAI Assistants API for command and controlhttps://www.microsoft.com/en-us/security/blog/2025/11/03/sesameop-novel-backdoor-uses-openai-assistants-api-for-command-and-control/