In one embodiment, a network security appliance includes a logic circuit, a network processing unit, and a general purpose processor to protect a computer network from malicious codes, unauthorized data packets, and other network security threats. The logic circuit may include one or more programmable logic devices configured to scan incoming data packets at different layers of a multi-layer protocol, such as the OSI-seven layer model. The network processing unit may work in conjunction with the logic circuit to perform protocol parsing, to form higher layer data units from the data packets, and other network communications-related tasks. The general purpose processor may execute software for performing functions not available from the logic circuit or the network processing unit. For example, the general purpose processor may remove malicious code from infected data or perform malicious code scanning on data when the logic circuit is not configured to do so.