The Internet Control Message Protocol (ICMP) provides many useful features to Network Administrators, primarily network troubleshooting ability.
Several ICMP options allow a user to gain information about the presence of network systems. These options are paired as requests and replies. The option pairs that provide this type of information are ICMP Echo Request/ICMP Echo Reply, ICMP Timestamp Request/ICMP Timestamp Reply, and ICMP Address Mask Request/ICMP Address Mask Reply.
Allowing remote users to transmit ICMP request or reply packets onto a local network could result in an exploit, resulting in an attacker developing a network map for targeting purposes. Administrators may consider filtering these types of ICMP messages at the perimeter
of the network, although doing so may impact network troubleshooting efforts.