Re:How Skype gets round firewalls
by jdbeast00 on Tuesday March 24, 2009 @09:08AM
(#530049)
"ie. to allow web surfing, a firewall will allow port 80, but most of the time it will allow both outbound and inbound 80"? outbound http traffic uses ephemeral ports, not 80.
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Outbound firewall rules almost never limit the source port, 99.99% of them only limit the destination port. If party A can accept packets on port 80 then almost any client out there can connect to the service on that port. The point being made is that a lot of default firewall rules allow traffic to any port 80 destination and accept traffic from any source to the local port 80.