Windows has a WSC (Windows Security Center) service that is used by antiviruses to tell Windows that another antivirus is present and to disable Windows Defender. This WSC API is not documented and, moreover, requires signing an NDA with Microsoft to obtain the documentation.
The original implementation of no-defender used third-party code provided by other AVs to register itself with WSC, while defendnot interacts with WSC directly.

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The original implementation of no-defender used third-party code provided by other AVs to register itself with WSC, while defendnot interacts with WSC directly.

download: