Kerberos is available in many commercial products as well. The Internet is an insecure place. Many of the protocols used in the Internet do not provide any security. Thus, applications which send an unencrypted password over the network 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.
Most of the really damaging incidents of computer crime are carried out by insiders. Firewalls also have a significant disadvantage in that they restrict how your users can use the Internet. In many places, these restrictions are simply unrealistic and unacceptable. 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.