Data Encryption Standard. It is a symmetric block cipher. More about DES can be found here. DES has been cracked by a custom machine called Deep Crack which cost $250,000 in 1998 and could brute force a DES key in 5 days. It is assumed that governments and military have similar machines for either a lot less cost or a lot more speed. DES has been replaced by the AES cipher because of it's weakness. Triple DES (3DES) which encrypts, decrypts and re-encrypts with either 2 keys or 3 keys is known to be a lot safer.