This is returned from the krb5_rd_safe() function. It means that the
checksum used to verify the data packet didn't match what was expected,
which would imply a corrupted data stream or a possible attack.

I have seen this occasionally when propagating our Kerberos database to
slave servers. As far as I can tell, it seems to be benign in this case. It
occurs very infrequently, I haven't had a chance to figure out what is going
on.