What is Kerberos and how does it work?

Kerberos is a network authentication protocol that uses symmetric key cryptography and a trusted third party called the Key Distribution Center, or KDC, to authenticate users without transmitting passwords over the network. The process works in three exchanges: the user authenticates to the Authentication Server and receives a Ticket Granting Ticket, or TGT. The user presents the TGT to the Ticket Granting Service to obtain a service ticket for the specific resource. The user presents the service ticket to the target server for access.