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Iran Blocks VPN Ports
First time accepted submitter Parham90 writes "After the Iranian post-election events that led to massive riots and break-outs through the world, the Iranian government started blocking all social websites, including Facebook, Youtube, Orkut, MySpace and Twitter. The Iranians, however, started using VPN (virtual private network) connections to bypass censorship. Since Thursday, September 30, 2011, all VPN ports have however been blocked, in the first attempt to start what the Iranian government calls the 'National Internet.'"
They could theoretically block everything but 80 and MITM any SSL connections (or did that cert get removed from IE yet?) to check those too, to prevent VPN connections that mimic HTTPS connections (real thing) and VPNs running over port 80 using deep-packet inspection. They'd also have to check for VPN over DNS (also, real thing). Short of this it's impossible to block VPNs.
Even then, you could run a VPN over a steganographic connection. In practice I find port 80 is the best - it's never failed me so far. 443 is a good option too, in fact a better option in theory, but keep in mind that a few mobile internet providers in 3rd world countries block 443.
"When information is power, privacy is freedom" - Jah-Wren Ryel
Hell, I once saw a VPN that rewrote its traffic to use ICMP messages and other nefarious means of communication in order to transmit packets.
It'd probably look odd if you KNEW to look at that individual's connection but the chances of finding *every* way that encrypted data can be slipped into another datastream are incredibly minimal.
Hell, VPN-over-HTTP-proxy is very common.
OpenVPN can use any port and is not detected as regular VPN communication, and can thus bypass firewalls that blocks VPN communication.
OpenVPN has not functioned properly in Iran for a while now, on any port. The same goes for Syria.
Unless I'm completely misunderstanding your comment, it doesn't matter what port its running on at all. Unless Iran is doing some seriously deep packet inspection, its not going to look "suspiscious." If you set your VPN peer to use port 80, its no longer an unencrypted HTTP port, its a VPN port. 80 being http is just a standard, but like everything, standards can be bent when necessary. As for doing DPI on every single IP device generating IP traffic into/out of the country, good farking luck. It'll basically wreck their international telecomm systems since most of those should be IP based by this point. DPI + UDP = crap audio.
OpenVPN can use any port and is not detected as regular VPN communication, and can thus bypass firewalls that blocks VPN communication.
OpenVPN was blocked even in 2010. No protocol (UDP or TCP) and port combination worked. Both normal and static key configuration were detected and blocked.
tcpdump showed a short packet exchange between the client and the server, and after that the connection completely died. Subsequent tries on the same protocol and port were completely blocked too (probably blacklisted).
Even so, I find it weird that OpenVPN was blocked while PPTP was allowed. Maybe they had/have a way of attacking PPTP ?
What worked back then and might still work is SSH (including tunneling). With access to a server outside Iran and a bit of imagination many things can be done with SSH tunneling.
The summary says Iran started internet censorship after the election and people started using VPN from then. No, it's not like that. First, internet censorship goes back to at 7 or 8 years, IIRC. Long before the election. Second, anti-censorship tools have always been changing in all these years. VPN is just the main tool of most of people now, but even two years ago (right after election) few people knew VPN and used other tools. So, things look tough, but it's not that we are going to lose our connection with the world. We always find a solution. Even right now I'm using a PPTP VPN and if you see this comment it works well. The only solution to prevent people from accessing sites the government doesn't like would be to shut down internet connection with the outside world completely. And I hope they won't do that, at least not for long.
"If fifty million people say a foolish thing, it's still a foolish thing."
I have tried SSH tunneling. Right now, that's how I am encrypting my connection. I've tried OpenVPN and PPTP and IpSec, and also L2TP. These are blocked (as far as I can gather). Haven't tried connecting to non-standard ports, however.
Unencrypted VPN traffic is incredibly easy to flag anyway, and even the handshake of popular encrypted VPN tunnels has a pattern that's predictable enough to be quite effective. I don't need to point out that ALL ports are affected. Switching to another port is basically useless in this context.
All this DPI doesn't require huge CPU processing power, as one would naively expect; since it (currently) happens only at the beginning of a session (yes, including UDP). And that is currently the Achilles' heel of this filter: if you initiate a "harmless" (as in allowed-by-policy) connection, and switch to encryption a couple of 10k packets later, you slip right through the firewall. Try it. If it doesn't work, they've upgraded to a new release and had to invest heavily in additional routers.
cpghost at Cordula's Web.