how do i stop defender smartscreen from blocking certain apps?

Unfortunately, AFAIK, you won't be able to selectively turn off SmartScreen for just one specific app. SmartScreen uses a system-wide reputation system to scan unrecognized executables. It either checks these files or it does not. Apps like alexeygrigorev/microboost on GitHub may be flagged because they are open-source and lack a Microsoft-issued code-signing certificate. As a result, they may not have an established reputation in Microsoft's database.

You can bypass this warning using two methods without disabling your overall system security.

Option 1: Permanently unblock the app file

When Windows downloads an app from the internet, it attaches a hidden tag called the Mark of the Web. Removing this tag can prevent SmartScreen from checking the file based on its downloaded status. Locate the Microboost executable file (.exe) in File Explorer. Right-click the file and select Properties. At the bottom of the General tab, look for a section labeled Security. Check the box labeled Unblock, then click Apply and OK. If you are running Microboost from a shortcut, make sure you perform these steps on the actual source .exe file rather than the shortcut icon.

Option 2: Add Microboost to Windows Defender exclusions

If removing the web tag does not stop the prompt, Windows Defender's real-time scanner might be interacting with the application. You can add an exclusion for the folder where Microboost is stored.

Open Windows Security from the Start menu. Click Virus & threat protection, then Manage settings under Virus & threat protection settings. Scroll down to Exclusions and click Add or remove exclusions. Click Add an exclusion and choose Folder or File. Select the file path where your Microboost application is stored.

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hth

Marcin