Do stateful packet filters keep track of any state information after the closure of a TCP connection and therefore, remember connections even after closing the connection?
My answer is NO. I don't see a need to do so. Alternatively, will there be any security threat if the stateful packet filter remembers closed connections? I can think that this state is limited and if the packet filter does not erase the data of closed connections, it won't be able to store state information of newer packets. This is some kind of DOS attack.