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.