Abstract: A method for detecting a malicious node in a network. The method includes obtaining a plurality of failed domain name service (DNS) queries from the network, wherein each of the plurality of failed DNS queries is initiated from a client node of the network and comprises an effective second-level domain (eSLD) name, generating, by a computer processor and using a pre-determined clustering algorithm, a cluster from a plurality of eSLD names comprising the eSLD name of each of the plurality of failed DNS queries, wherein the cluster comprises a portion of the plurality of eSLD names that is selected based on the pre-determined clustering algorithm, determining, by the computer processor and using a pre-determined formula, a score representing statistical characteristics of the cluster, and assigning, in response to the score meeting a pre-determined criterion, a malicious status to the client node.