Abstract
Effective mitigation of denial of service (DoS) attack is a pressing problem on the Internet. In many instances, DoS attacks can be prevented if the spoofed source IP address is traced back to its origin which allows assigning penalties to the offending party or isolating the compromised hosts and domains from the rest of the network. IP traceback mechanisms based on probabilistic packet marking (PPM) have been proposed for achieving traceback of DoS attacks. We show that probabilistic packet marking-of interest due to its efficiency and implementability vis-a-vis deterministic packet marking and logging or messaging based schemes-suffers under spoofing of the marking field in the IP header by the attacker which can impede traceback by the victim. We show that there is a trade-off between the ability of the victim to localize the attacker and the severity of the DoS attack, which is represented as a function of the marking probability, path length, and traffic volume. The optimal decision problem-the victim can choose the marking probability whereas the attacker can choose the spoofed marking value, source address, and attack volume-can be expressed as a constrained minimax optimization problem, where the victim chooses the marking probability such that the number of forgeable attack paths is minimized. We show that the attacker's ability to hide his location is curtailed by increasing the marking probability, however, the latter is upper-bounded due to sampling constraints. In typical IP internets, the attacker's address can be localized to within 2-5 equally likely sites which renders PPM effective against single source attacks. Under distributed DoS attacks, the uncertainty achievable by the attacker can be amplified, which diminishes the effectiveness of PPM
