Remote Denial of Service Attacks and Countermeasures

As evinced by a series of high profile attacks, denial of service (DoS), or prevention of legitimate access to resources, is a threat that demands attention. Of particular concern are distributed attacks, in which an adversary recruits several computers to aid in the attack. The first major distributed denial of service (DDoS) attack brought down the University of Minnesota’s network for three days in August 1999. About six months later, the attack by a Canadian teenager on several major sights including Yahoo, Amazon, eBay, CNN, and Buy.com made headlines. In accord with the underlying principle that destruction is simpler than construction, denial of service attacks come in many forms and are easy to carry out, but preventing them can sometimes be tricky. Although there is no panacea for all flavors of denial of service, there are several countermeasures that focus on either making the attacks more difficult or on making the attacker accountable via logging and tracing.