Some USB drives use various methods to secure the precious data on the memory stick, but these software methods only logically lock the drive or encrypt its contents. One of the problems with a software method is that the protection can be circumvented by using another OS or running a password-checking program.
Corsair has delivered an answer to this problem with their Padlock line of USB flash drives. These drives use a physical numeric keypad, combined with a hardware mechanism to lock or unlock the drive before use. Once locked, no computer will be able to use it, regardless of the platform. The hardware protects the drive at its lowest level, so not even a drive letter is mapped.