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Passive Detection of Misbehaving Name Servers

October 2013 Technical Report
Leigh B. Metcalf, Jonathan Spring

In this report, the authors explore name-server flux and two types of data that can reveal it.


Software Engineering Institute

CMU/SEI Report Number


DOI (Digital Object Identifier):


In the process of categorizing malicious domains, distinguishing between suspicious and benign name servers can allow the name servers themselves to be acted against. Name servers do not normally change internet protocol (IP) addresses frequently. Domains that do change IP addresses quickly or often are said to exhibit IP flux, which can allow services, such as web pages that deliver malicious content, to circumvent defenders' attempts to block their IP addresses. IP flux in a name server's domain may be a sign that the name server is suspicious. This report demonstrates that name-server flux exists and is ongoing. Furthermore, there are two types of data that can reveal IP flux in domain name system (DNS) servers: passively collected DNS messages and the contents of several large, top-level domains' official zone files.