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.


  • Interesting... can you post the output of iptables-save?
    – pepoluan
    Jan 3, 2014 at 15:43
  • @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.
    – saelic
    Jan 3, 2014 at 16:00

1 Answer 1


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.

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