NS record History Based Abnormal DNS traffic Detection Considering Adaptive Botnet Communication Blocking

Abstract

DNS (Domain Name System) based name resolution is one of the most fundamental Internet services for both of the Internet users and Internet service providers. In normal DNS based name resolution process, the corresponding NS (Name Server) records are required prior to sending a DNS query to the authoritative DNS servers. However, in recent years, DNS based botnet communication has been observed in which botnet related network traffic is transferred via DNS queries and responses. In particular, it has been observed that, in some types of malware, DNS queries will be sent to the C&C servers using an IP address directly without obtaining the corresponding NS records in advance. In this paper, we propose a novel mechanism to detect and block abnormal DNS traffic by analyzing the achieved NS record history in intranet. In the proposed mechanism, all DNS traffic of an intranet will be captured and analyzed in order to extract the legitimate NS records and the corresponding glue A records (the IP address(es) of a name server) which will be stored in a white list database. Then all the outgoing DNS queries will be checked and those destined to the IP addresses that are not included in the white list will be blocked as abnormal DNS traffic. We have implemented a prototype system and evaluated the functionality in an SDN-based experimental network. The results showed that the prototype system worked well as we expected and accordingly we consider that the proposed mechanism is capable of detecting and blocking some specific types of abnormal DNS-based botnet communication.