Hackers built a ‘master key’ for millions of hotel rooms

Any key card will do. Even old and expired, or discarded keys retain enough residual data to be used in the attack. Using a handheld device running custom software, the researchers can steal data off of a key card — either using wireless radio-frequency identification (RFID) or the magnetic stripe.

That device then manipulates the stolen key data, which identifies the hotel, to produce an access token with the highest level of privileges, effectively serving as a master key to every room in the building.

Source: zdnet.com