The Evil Maid Attack is a form of a bootable USB stick image that allows to perform the attack in an easy plug-and-play way. The whole infection process takes about 1 minute, and its well suited to be used by hotel maids. The current implementation of Evil Maid always stores the last passphrase entered, assuming this is the correct one, in case the user entered the passphrase incorrectly at the first attempt. It’s probably illegal to use Evil Maid to obtain the passphrases from other people without their consent.”]
Source: http://theinvisiblethings.blogspot.com/2009/10/evil-maid-goes-after-truecrypt.html