A denial of service (DoS) attack is an attempt by a person or a group of persons to cripple an online service. This can have serious consequences on companies like Amazon and eBay, which rely on their online availability to do business. Many defense mechanisms have been proposed to thwart DoS attacks. One of these defense mechanisms is called hop-count filtering. Although an attacker can forge any field in the IP header, he or she cannot falsify the number of hops an IP packet takes to reach its destination. This hop-count information can be inferred from the time-to-live value in the IP header. ...