Without knowledge of the identity of an individual requesting an operation,
it is often difficult to decide whether the operation should be allowed.
Traditional authentication methods are not suitable for use
in computer networks where attackers can monitor network traffic and
intercept passwords. The use of strong authentication methods that do
not disclose passwords is imperative. The Kerberos authentication
system supports strong authentication on such networks.
for IETF Kerberos working group web page.