A brand new software known as ‘Defendnot’ can disable Microsoft Defender on Home windows units 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 mechanically disables Microsoft Defender to keep away from conflicts from operating a number of safety purposes on the identical machine.
The Defendnot software, created by researcher es3n1n, abuses this API by registering a pretend antivirus product that meets all of Home windows’ validation checks.
The software relies on a earlier undertaking known as no-defender, which used code from a third-party antivirus product to spoof registration with WSC. That earlier software was pulled from GitHub after the seller filed a DMCA takedown.
“Then, after a number of weeks after the discharge, the undertaking 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 need to do something with that so simply erased all the pieces and known as it a day,” the developer explains in a weblog submit.
Defendnot avoids copyright points by constructing the performance from scratch via a dummy antivirus DLL.
Usually, WSC API is safeguarded via Protected Course of Mild (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 title.
As soon as registered, Microsoft Defender instantly shuts itself off, leaving no energetic safety on the machine.
Supply: BleepingComputer
The software additionally features a loader that passes configuration information through a ctx.bin file and allows you to set the antivirus title you need to use, flip off registration, and allow verbose logging.
For persistence, Defendnot creates an autorun via the Home windows Job Scheduler in order that it begins while you log in to Home windows.
Whereas Defendnot is taken into account a analysis undertaking, the software demonstrates how trusted system options could be manipulated to show off safety features.
Microsoft Defender is at the moment detecting and quarantining Defendnot as a ‘Win32/Sabsik.FL.!ml; detection.
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