This paper looks at the evolution of firewall technology towards Deep Packet Inspection, and then discusses some of the security issues with this evolving technology.

Microsoft, Cisco, Checkpoint, Symantec, Nortel, SonicWall, NAI, Juniper/Netscreen, and others, have, in the past eighteen months started manufacturing firewall appliances that implement Deep Packet Inspection (DPI). In general, the DPI engine scrutinizes each packet (including the data payload) as it traverses the firewall, and rejects or allows the packet based upon a ruleset that is implemented by the firewall administrator. The inspection engine implements the ruleset based upon signature-based comparisons, heuristic, statistical, or anomaly-based techniques, or some combination of these.

By Dr. Thomas Porter at SecurityFocus.

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