Revealed earlier this month
, Valve's Steam Guard security features have now been activated on the Steam client.
Steam Guard allows users to link their account to a specific PC, after which any attempts to login to your account from a different computer will notify the owner of the account, and request their approval.
An email is sent to the specified address, asking for the user's permission to let a different PC access the account.
The new features do not yet take advantage of Intel's Identity Protection Technology solution, although Valve says that it "hopes to offer additional forms of authentication soon."
The security features are available to anyone with a 2nd Generation Intel Core or Intel Core vPro processor. Third party developers will be able to incorporate Steam Guard into their applications through Steamworks.
Steam Guard will be automatically activated as default when your Steam client next updates itself.
The security status of users' clients can be found under 'Settings', and Steam Guard can be deactivated and reactivated at any time.