Hardware-based full disk encryption

Hardware-based full disk encryption (FDE) is available from many hard disk drive (HDD/SSD) vendors, including Kingston Technology, Integral Memory, iStorage Limited, Micron, Seagate Technology, Sandisk, Samsung, Toshiba, Viasat UK, and Western Digital. The symmetric encryption key is maintained independently from the computer's CPU, thus allowing the complete data store to be encrypted and removing computer memory as a potential attack vector.

Source: Wikipedia — Hardware-based full disk encryption (CC BY-SA 4.0)