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Windows Defender MpClient.dll Loaded by Non-Defender Process

The following analytic detects mpclient.dll, the Windows Defender client API library, being loaded by a process that is not part of the Windows Defender platform. mpclient.dll exposes the API surface used to drive…

Description

The following analytic detects mpclient.dll, the Windows Defender client API library, being loaded by a process that is not part of the Windows Defender platform. mpclient.dll exposes the API surface used to drive on-demand Defender scans (IOAV, MpScan). In the ShieldBreak exploit, the attacker binary loads mpclient.dll directly and calls its scan APIs against an object-manager path in order to trigger a Defender scan against attacker-controlled content as part of a race condition targeting Defender's placeholder-hydration behavior. If confirmed malicious, this activity indicates an attempt to weaponize Windows Defender's own scanning pipeline for local privilege escalation.

Detection logic

Detection requirements

Platform
ContainersLinuxmacOSWindows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
sysmon_eventid_7

Known benign triggers

  • Third-party security products or custom AV-integration tooling that legitimately calls into the Defender client API may load mpclient.dll outside the Defender platform directories. Filter as necessary for your environment.

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