Abstract

DNS protocol is critically important for secure network operations. All networked applications request DNS protocol to translate the network domain names to correct IP addresses. The DNS protocol is prone to attacks like cache poisoning attacks and DNS hijacking attacks that can lead to compromising user’s accounts and stored information. In this paper, we present an anomaly based Intrusion Detection System (IDS) for the DNS protocol (DNS-IDS) that models the normal operations of the DNS protocol and accurately detects any abnormal behavior or exploitation of the protocol. The DNS-IDS system operates in two phases, the training phase and the operational phase. In the training phase, the normal behavior of the DNS protocol is modeled as a finite state machine where we derive the temporal statistics of normal DNS traffic. Then we develop an anomaly metric for the DNS protocol that is a function of the temporal statistics for both the normal and abnormal transitions of the DNS protocol. During the operational phase, the anomaly metric is used to detect DNS attacks (both known and novel attacks). We have evaluated our approach against a wide range of DNS attacks (DNS hijacking, Kaminsky attack, amplification attack, Birthday attack, DNS Rebinding attack). Our results show attack detection rate of 97% with very low false positive alarm rate (0.01397%), and round 3% false negatives.