You can perform an offline scan with Windows Defender in Windows 10 build 14271
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An offline version of Windows Defender has been spotted in the Windows 10 Insider Preview. If you're rocking build 14271, it's possible to reboot the installation into a more secure mode to begin scanning the PC for threats to be removed without requiring the program to be on external storage.
There'll be a new option in the Settings app (under Security + Updates > Windows Defender) that will allow you to select "Scan Offline". This will cause the system to reboot and is estimated to take around 15 minutes to complete. It's a neat feature for those who choose Defender as their main line of protection.
Source: Comms1; via: WinCore.ru; Thanks, @craftuser, for the tip!
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Rich Edmonds was formerly a Senior Editor of PC hardware at Windows Central, covering everything related to PC components and NAS. He's been involved in technology for more than a decade and knows a thing or two about the magic inside a PC chassis. You can follow him on Twitter at @RichEdmonds.