An intrusion detection and prevention (IDP) device includes an attack detection module and a forwarding component. The attack detection module applies a compound attack definition to a packet flow of a computer network to determine whether the packet flow includes at least one pattern and at least one protocol anomaly. The forwarding component selectively discards the packet flow based on the determination. The IDP device may further include a reassembly module to form application-layer communications from the packet flows, and a plurality of protocol-specific decoders to process the application-layer communications to extract application-layer elements and detect protocol anomalies.