An attacker sends an ICMP type 13 Timestamp Request to determine the time
						as recorded by a remote target. Timestamp Replies, ICMP Type 14, usually
						return a value in Greenwich Mean Time. An attacker can attempt to use an
						ICMP Timestamp requests to 'ping' a remote system to see if is alive. An
						attacker may be able to use the timestamp returned from the target to attack
						time-based security algorithms, such as random number generators, or
						time-based authentication mechanisms. Additionally, because these types of
						messages are rare they are easily spotted by intrusion detection systems.
						Many ICMP scanning tools support IP spoofing to help conceal the origin of
						the actual request among a storm of similar ICMP messages. It is a common
						practice for border firewalls and gateways to be configured to block ingress
						ICMP type 13 and egress ICMP type 14 messages.