stateful

Following on from Eric Byres’ discussion of Deep Packet Inspection (DPI), this article discusses a second and equally important aspect of effective firewall security referred to as “stateful inspection”.

Over the years I have been asked by a number of control engineers, “Our IT dept says we have VLANs, so why do I need a firewall?”

Back in the mid-90s, I was a big supporter of Virtual Local Area Networks (VLANs) for security. Unfortunately, I have seen so many issues with this technology that I no longer believe it provides effective security.