1. Any type of system on the network that can be used to amplify (increase) the the size of traffic is known as an amplifier. Example: The classic example is the smurf amplifier. An attacker spoofs the address of a victim and sends directed broadcasts to the amplifier, which then sends hundreds of replies back to the victim. Thus, it only costs the attacker a single packet to send many packets to the victim. Example: A more subtle attack is the use of DNS. The DNS response packet can be much larger than the request. This allows an attacker to flood the victim with large packets at the cost of small packets. From Hacking-Lexicon