Re: attack on a computer behind a nat.

Shreyas Zare wrote:

Thats precisely Simple Traversal of UDP through NAT (STUN) protocol. I
believe that only UDP can be exploited with some success and TCP will
be almost impossible unless you compromise the NAT box itself.

Pretty much, yes.
Normally, an outbound tcp will be just that - a port opened at random by
a program to perform an outbound (originating) tcp handshake and
conversation; it won't be expecting to receive an inbound tcp handshake
on that port, and usually will just drop packets of that type.
udp ports are much more likely to accept random packets from places they
aren't expecting them to come from.

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