so I read this thread about port-knocking (altough called "reflexsive
firewalls"). I'd never heard of that and found that to be an very
interesting mechanism. Now I just keep wondering, what an attacker
could possibly do to intrude system secured in such a way. So there
are no open ports at all, also, there's no way the attacker could
access the computer physically or via social engineering. The
attacker knows that a knock-server is running and that there's some
daemon waiting to become accessible (what ever that may be).
What could a attacker do to somehow get access to that machine? And
how can I secure that machine from that kind of attacks.