A brand new instrument known as ‘Defendnot’ can disable Microsoft Defender on Home windows gadgets by registering a pretend antivirus product, even when no actual AV is put in.
The trick makes use of an undocumented Home windows Safety Middle (WSC) API that antivirus software program makes use of to inform Home windows it’s put in and is now managing the real-time safety for the machine.
When an antivirus program is registered, Home windows routinely disables Microsoft Defender to keep away from conflicts from operating a number of safety functions on the identical machine.
The Defendnot instrument, created by researcher es3n1n, abuses this API by registering a pretend antivirus product that meets all of Home windows’ validation checks.
The instrument relies on a earlier venture known as no-defender, which used code from a third-party antivirus product to spoof registration with WSC. That earlier instrument was pulled from GitHub after the seller filed a DMCA takedown.
“Then, after a couple of weeks after the discharge, the venture blew up fairly a bit and gained ~1.5k stars, after that the builders of the antivirus I used to be utilizing filed a DMCA takedown request and I did not actually wish to do something with that so simply erased every little thing and known as it a day,” the developer explains in a weblog submit.
Defendnot avoids copyright points by constructing the performance from scratch by means of a dummy antivirus DLL.
Usually, WSC API is safeguarded by means of Protected Course of Gentle (PPL), legitimate digital signatures, and different options.
To bypass these necessities, Defendnot injects its DLL right into a system course of, Taskmgr.exe, that’s signed and already trusted by Microsoft. From inside that course of, it could actually register the dummy antivirus with a spoofed show identify.
As soon as registered, Microsoft Defender instantly shuts itself off, leaving no energetic safety on the machine.
Supply: BleepingComputer
The instrument additionally features a loader that passes configuration information through a ctx.bin file and allows you to set the antivirus identify you wish to use, flip off registration, and allow verbose logging.
For persistence, Defendnot creates an autorun by means of the Home windows Job Scheduler in order that it begins once you log in to Home windows.
Whereas Defendnot is taken into account a analysis venture, the instrument demonstrates how trusted system options will be manipulated to show off security measures.
Microsoft Defender is presently detecting and quarantining Defendnot as a ‘Win32/Sabsik.FL.!ml; detection.
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