US Patent 9398043 Applying fine-grain policy action to encapsulated network attacks

An intrusion detection system inspects encapsulated packet flows and, upon detecting a malicious encapsulated packet flow, may close an encapsulated network session corresponding to the malicious flow or drop sub-packets of the malicious flow without acting against non-malicious sub-packets and/or sessions. In one example, a network device includes a flow analysis module that receives a packet flow packets, each packet comprising a packet header and one or more sub-packets each corresponding to respective network sessions, an attack detection module that identifies at least one of the network sessions as a malicious network session, a policy action module that executes a policy action on the sub-packet corresponding to the malicious network session based on the identification of the malicious network session, and a forwarding component that forms a reconstructed packet comprising the packet header and the sub-packets excluding the sub-packet corresponding to the malicious network session and forwards the reconstructed packet.