1. The authentication system of MIT's Project Athena. It is based on symmetric key cryptography. Adopted by OSF as the basis of security for DME. From Linux Guide @FirstLinux

2. An authentication standard. History: Developed at MIT in the 1980s as part of its project Athena (the netpc product that also spawned X Windows and other technologies). Kerberos has long been available as an add-on to virtually all UNIX systems. Version 4 was discovered to be insecure, and was followed by version 5. Microsoft implemented a variant of version 5 in Win2k. Key point: Microsoft's implementation in Win2k is not quite standard in much the same way that its implementations of PPP, PPTP, IPsec, etc. all make use of proprietary extensions. Kerberos: DES From Hacking-Lexicon