How does uTorrent can automatically forward port through Linux Net Filter based firewall?

3

I have dilemma: How it is possible that uTorrent shows on my internal machine with internal IP, that my connection is OK (green check in the bottom right of its window), while I never forwarded any port. I have Linux based PC on the edge of my network, default Kernel, strict iptables rules and never done anything with UPNP or NAT-PMP.

It looks like security vulnerability. I would like to deny such possibility. Thank you very much for help.

Saelic

Mark Saelic

Posted 2014-01-03T15:40:17.630

Reputation: 131

Interesting... can you post the output of iptables-save? – pepoluan – 2014-01-03T15:43:11.520

@pepoluan There is really nothing special: INPUT & FORWARD policy set to DROP, simple rules like: -A FORWARD -i eth1 -o eth0 -j ACCEPT and -A FORWARD -i eth0 -o eth1 -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT I'm not novice to iptables, I carefully audited my configuration and still don't know how it is possible. – Mark Saelic – 2014-01-03T16:00:00.153

Answers

0

I sometimes saw the same glitch on uTorrent without port forwarding.

However, when I use port forwarding on my gateway computer, the latest uTorrent doesn't see it, as it tries NAT-PMP and UPnP which are not available on the gateway.

So don't bother, the open port feature works only with computers directly connected to internet or with computers behind routers the have UPnP enabled.

machineaddict

Posted 2014-01-03T15:40:17.630

Reputation: 85

Asked: 2014-01-03T15:40:17.630

Viewed: 568 times

Active: 2014-02-13T23:52:31.510