Kerberos is based on the key distribution model presented by Needham and Schroeder. It allows entities communicating over networks to prove their identity to each other while preventing eavesdropping or replay attacks. Many of the protocols used in the Internet do not provide any security. Thus, applications which send a password over the network unencrypted are extremely vulnerable. Other applications rely on the client to restrict its activities to those which it is allowed to do, with no other enforcement by the server.
Some sites attempt to use firewalls to solve their network security problems.
The majority of the more damaging incidents of computer crime have been carried out by insiders. Firewalls also have a significant disadvantage in that they restrict how your users can use the Internet. Kerberos was created by MIT as a solution to these network security problems. After a client and server has used Kerberos to prove their identity, they can also encrypt all of their communications to assure privacy and data integrity as they go about their business. Kerberos is freely available from MIT, under a copyright permission notice very similar to the one used for the BSD operating and X11 Windowing system.