Antidotes for DNS Poisoning by Off-Path Adversaries

Following to Kaminsky´s attack (2008), cachingresolvers were patched with defenses against poisoning. So far, the main improvements were non-cryptographic and easy todeploy (requiring changes only in resolvers). Some of these improvements are widely deployed, and it is believed that they suffice to prevent poisoning, at least by off-path, spoofingattackers. We perform a critical study of the prominent defense mechanisms against poisoning attacks by off-path adversaries. We present weaknesses and limitations, and suggest counter-measures. Our main message is that the DNS infrastructure shouldnot rely on short term, ´easy-to-deploy´ defenses, and efforts should be increased towards transition to DNSSEC.