07. ICMP (Internet Control Message Protocol)

• Support protocol used for network diagnostics.

• Sends control messages, like error reports or operational info.

• Echo request/reply: used by ping to test reachability.

• ICMP redirect: special message used by routers to correct inefficient routing paths (for example in the triangular routing scenario).

traceroute: “Destination unreachable”, “Time exceeded”, etc.

Smurf Attack

• An attacker sends a large number of ICMP requests to a network’s broadcasting address while spoofing the source IP to be the victim’s.
• All active hosts reply to the victim, overwhelming it with traffic.
• 192.168.3.255 is the broadcast address.