AP® Cybersecurity glossary
Internet control message protocol (ICMP)
Also called: ICMP
A protocol for short test and error messages between devices, used by ping; it has no port numbers.
Appears in the course and exam description (CED): 3.1.A.43.1.C.53.5.E.6
Why it matters in Unit 3
ICMP is the protocol of a smurf attack, and an external firewall that does not block ICMP from outside is rated a moderate risk.
Example
ping 192.168.1.1 sends an ICMP echo request; the router answers with an echo reply and the round-trip time.
Learn it properly, with a checkpoint Addresses: MAC, IP, ARP, DNS and ICMP