Smurf attack
The smurf attack, named after its exploit program, is a denial-of-service attack which uses spoofed broadcast ping messages to flood a target system.In such an attack, a perpetrator sends a large amount of ICMP echo (ping) traffic at IP broadcast addresses, all of it having a spoofed source address of a victim. If the routing device delivering traffic to those broadcast addresses performs the IP broadcast to layer 2 broadcast function, most hosts on that IP network will take the ICMP echo request and reply to it with an echo reply each, multiplying the traffic by the number of hosts responding. On a multi-access broadcast network, there could potentially be hundreds of machines to reply to each packet.
Several years ago, most IP networks could be thus used in smurf attacks -- in the lingo, they were "smurfable". Today, thanks largely to the ease with which a network can be made immune to this abuse, very few networks remain smurfable. [1]
To secure a network with a Cisco router from being used in a smurf attack, the router command no ip directed-broadcast will suffice.
