Security Question

The following text is taken from the SFS FAQ
(http://www.fs.net/sfswww/sfsfaq.html):
"AFS, another widely-used network file system, does
not keep the contents of private files secret from
network eavesdroppers. Moreover, AFS uses an insecure
message authentication code (MAC) to protect the
integrity of communication between clients and
servers. An active attacker can, with very little
computation, tamper with and change the contents of
AFS messages in transit."

Based on my high level understanding of Kerberos (used
by AFS), once the users have obtained credentials and
are authenticated the traffic between parties is
securely transmitted.  This seems to clash with the
statements in the FAQ.  Is there further documentation
to be read or can someone explain this?




	
		
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