Abstract: In one embodiment, a DNS security network includes several DNS appliances and a security operations center (SOC) server computer. The SOC server computer may receive telemetry data from the DNS appliances, the telemetry data comprising information about DNS client queries received in the respective DNS appliances. From the telemetry data, the SOC server computer may generate security policies for distribution to the DNS appliances. The security policies may be used by the DNS appliances to determine whether a DNS client query is originated by a client computer performing a prohibited activity (e.g., sending spam, communicating with a zombie control computer, navigating to a prohibited website, etc.). An answer to a client query may be replaced or discarded altogether in cases where the originator is performing a prohibited activity.

Abstract: In one embodiment, a transparent relay receives diverted e-mail communications between an e-mail client and an e-mail server. The transparent relay may be configured to examine the e-mail communications for network security policy violations. E-mail communications that do not violate a network security policy may be relayed to their intended destination. Policy actions, such as discarding or redirection, may be performed on those that violate one or more network security policies. The transparent relay may include a pair of communications interfaces running in promiscuous mode, one for downstream communications and another for upstream communications. The transparent relay may decompose a network communication protocol to look network security policy violations.