icmp timestamps
Thursday, December 14th, 2006The Timestamp is an ICMP (rfc792) message which is used for time synchronization. The Timestamp Reply message consists of the originating timestamp sent by the sender of the Timestamp as well as a receive timestamp and a transmit timestamp.
If your machine answers ICMP Timestamp messages an attacker can learn the date which is set on your machine. This may help him to defeat all your time based authentication protocols.