Cache-Property-Aware Features for DNS Tunneling Detection

A lot of enterprises are under threat of targeted attacks causing data exfiltration. As a means of performing the attacks, attackers and their malware have exploited DNS tunneling in recent years. Although there are many research efforts to detect DNS tunneling, the previously proposed methods rely on features that the malicious entities can easily obfuscate by mimicking legitimate ones. Therefore, this obfuscation would result in data leakage. In order to mitigate this issue, we focus on a trace of DNS tunneling, which cannot be easily hidden. In the context of DNS data exfiltration, malware connects directly to the DNS cache server, and a DNS tunneling query produces a cache miss with absolute certainty. In this work, we propose features derived from this cache property. Our extensive experiments show that one of the proposed features can clearly distinguish DNS tunneling traffic, which makes it useful to design and implement a solid DNS firewall against DNS tunneling.