Is “Microsoft Safety Scanner” an add-on (extension) or an independent antivirus software? If it’s an add-on, then would it work in combination with any antivirus software?
It's an optional scanner to use as if and when.
Microsoft Safety Scanner
The Microsoft Safety Scanner is not a replacement for using an antivirus software program that provides ongoing protection.
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Hello, Microsoft security scanner is an executable file that can work besides your antivirus of choice. Keep in mind that once you download the file, it is only good for 10 days. If you need to use it for more time than that, you have to redownload the file so that it includes the latest signatures.