Using SSH to hide Skype trafic

**BoredBloke** · 28 February 2007, 11:43

No, but which ones don't allow it?

**snaw** · 28 February 2007, 18:39

Originally posted by portseven

Has anyone used SSH and Dynamic Port Forwarding (SOCKS Emulation) to hide Skype trafic from ISP's who dont allow voice trafic?

Your problem is going to be that by encrypting the packet using ssh you're adding to the packet size, whcih in turn will affect the delay and jitter which I'm guessing will make your skype close to unusable. Not quite sure what you're trying to do with the port forwarding, skype uses random ports anyway (Same ones for duration of call but random apart from that). They'll be able to spot skype no matter what port you use based on the traffic profile - voice is pretty unique.

**AtW** · 28 February 2007, 18:50

Originally posted by snaw

Your problem is going to be that by encrypting the packet using ssh you're adding to the packet size, whcih in turn will affect the delay and jitter

Quiet.

snaw is a local expert on latency issues, so if he says something about it then it must be right.

**snaw** · 28 February 2007, 18:56

Yep, though I bow to AtW's superior knowledge on, well on everything really. He really is the dog's bollocks.

**portseven** · 1 March 2007, 08:41

Originally posted by snaw

Your problem is going to be that by encrypting the packet using ssh you're adding to the packet size, whcih in turn will affect the delay and jitter

Point taken, I think I will do some experimenting this weekend. See how it goes.

Originally posted by snaw

Not quite sure what you're trying to do with the port forwarding, skype uses random ports anyway

Skype aparently can use SOCKS v4/5 proxying and when you use dynamic port forwarding on ssh (ssh -D 1234 remote_server) it effectivly sets up a SOCKS Proxy listening on localhost:1234 (the 1234 can be any port number you chose). So as far as the ISP concerned all they see is a ssh session going out of their network. Though like you say the trafic profile might stand out as voice, but do they monitor like that or do they look at source / destination ports?

The reason for asking is for the 3G ISP's, some have a flat rate but charge a higher flat rate if you want to do stuff like VoIP, my question is how do they know you are using VoIP? And can you disguise it?

**snaw** · 1 March 2007, 09:21

Originally posted by portseven

Skype aparently can use SOCKS v4/5 proxying and when you use dynamic port forwarding on ssh (ssh -D 1234 remote_server) it effectivly sets up a SOCKS Proxy listening on localhost:1234 (the 1234 can be any port number you chose). So as far as the ISP concerned all they see is a ssh session going out of their network. Though like you say the trafic profile might stand out as voice, but do they monitor like that or do they look at source / destination ports?

The reason for asking is for the 3G ISP's, some have a flat rate but charge a higher flat rate if you want to do stuff like VoIP, my question is how do they know you are using VoIP? And can you disguise it?

Not sure what you'll achieve by encapsulating your skype packets in ssh, even if you don't an ISP won't be able to recognise skype packets based on port number as it's a random port number. They will be able to recognise it if they have the right tools in place however based on it's traffic profile. Can't answer if they will monitor - really depends on what they have set up - which I imagine they have already if they're billing you. No way you can disguise the traffic profile without impacting your call, voice is pretty unique in that respect.

Worth trying to see, but I suspect you'll not get the answer you want.

Using SSH to hide Skype trafic