There are plenty of online services that use two-factor authentication to reduce the chances of someone hijacking your account after a data breach, but what about the operating system on your PC or phone? You'll get that safeguard if you use Windows 10, according to a Microsoft security brief. The new OS will optionally treat a device (including something nearby, like your phone) as one authentication factor when signing into a local or internet account, and a PIN code or biometric reader as the second. If hackers find your login data sitting on a server, they won't get to use it unless they also have your gear -- and in some cases, they may need a fake fingerprint as well.