1. A method of detecting malicious behavior on a network, the method comprising: performing malicious partial signature detection by reading the contents of packets of data passing through the network to look for partial signatures associated with malicious programs, each partial signature having a size that is at most the size of a given packet passing through the network; monitoring the Domain Name Service, DNS, requests made by hosts connected to the network and/or responses thereto; analyzing the results of the partial signature detection and the DNS monitoring; making a determination of the suspected presence of malicious behavior on the network based upon an analysis of the results of both the partial signature detection and the DNS monitoring; and in response to a determination that malicious behavior is present, blocking packets exhibiting the malicious behavior.