[Shorewall-users] Overnet and Shorewall

John Pettigrew john at xl-cambridge.com
Fri Oct 24 15:04:57 PDT 2003

I've just started using Overnet (a p2p app) on my SusE 8.2 box. The box is
protected with shorewall and has been for some time with no problems. However,
I was surprised to see that I am actually uploading files to other Overnet
users without explicitly opening any ports. I've checked with grc.com's
ShieldsUp and there don't seem to be any open ports, including port 4662,
which is what overnet is using - certainly, Shorewall is configured to DROP
all packets from the net to the fw. Indeed, in my firewall log, I do see
packets from outside to port 4662 being DROPped by shorewall.

Is anyone familiar with the overnet program? How is it getting past the
firewall on my linux box? The linux version doesn't seem to have the feature
some similar apps do in Windows, of telling you whether it thinks you're
firewalled, so there's no help from it.

All I can think is that it is sending files only to clients from which I have
started receiving files, so the connection is already established. It would
ease my mind greatly if this was all that was happening! Perhaps overnet opens
connections with all other clients when it searches them for files, and these
stay open, allowing the remote clients to upload from me?


John Pettigrew          XL Cambridge - contract and freelance editing
Biology specialist         Molecular biology, genetics, biotechnology
john at xl-cambridge.com                    http://www.xl-cambridge.com/
PGP public key available

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