Extraído do site da samsung :
AES encryption is always active on an 840 or 840 Pro Series SSD. In order to benefit from the encryption feature, however, the user must enable an ATA password to limit access to the data. Failure to do so will render AES-encryption ineffective – akin to having a safe but leaving the door wide open.
To set an ATA password, simply access the BIOS, navigate to the “Security” menu, enable “Password on boot” and set an “HDD Password.”