In the same vein as our recent Defcon article on biometric cloning, White Wolf Security has released this article about turning a biometric door lock into a trojan. They note that there are many common ways to break into one, from harvesting fingerprints to using gummy bears to fake a finger. This hack involves having full access to the unit so you can disassemble it.
The unit has a system built-in where you can touch a 9-volt battery to some connectors on the bottom to power it in case of a building power failure. The researchers simply routed some wires from the motorized lock to the plates used for the 9-volt and then reassembled the lock. The door can then be opened at any time without verification, even if the software on the unit is reset.