Let me start by stating that much of what I’m about to cover was seeded by a wonderful talk I heard by Marcus Ranum back in 2003. Since then I’ve been sort of mulling everything over, and here are the basic ideas: From Marcus’s talk: Q: What does a packet filter do? A: Looks at a few parts…
China Illustrates How Not To Do Firewall Filtering
Someone’s noticed a very interesting fact about firewall filtering that relies on session sniping, i.e. killing connections with RST packets. Namely, it’s rather trivial to bypass. For those who are into this sort of thing, the idea is very simple. China blocks people from going to certain sites by having their firewall kill browser sessions that contain certain…