Smurf
A common technique of performing a DoS (Denial of Service) attack -- but one that takes a different approach to the usual DoS routine. DoS would normally use default pings to overwhelm a given host. But to really overwhelm the resources of a given target, the attacker would have to compromise many computers, and have them ping the target simultaneously.
The difference that Smurf provides is the ability to launch a DoS against a target from only a single computer. Smurf works by sending a ping packet to the broadcast address of a network, using a spoofed source IP address. The source IP address is the actual target. When all the clients of the network respond to the ping packet, they will all be sending a reply to the single spoofed address. It is this multiple response that is the actual DoS attack, overwhelming the spoofed target system.
source:
http://www.itsecurity.com/dictionary/smurf.htm