Groups | Search | Server Info | Login | Register

Groups > comp.security.misc > #260

Re: How to detect a VPN connection?

Show all headers | View raw

Gilles <nospam@nospam.com> writes:
>I just read this article:

>"The latest information indicate that now Syria is also following
>China and Iran in blocking VPN ports on the internet to limit user
>access."

>www.stopfundamentalism.com/index.php?option=com_content&task=view&id=1207&Itemid=

>How do admins detect VPN connections? Because the TCP/IP packets have
>some particular header?

FWIW: I was in China in Fall 2010 and had zero problems connecting on
any VPN type I tried in 4 different cities within China. Nor did I 
have any problems in 2004 when I was there as well.

Of course, the great firewall did block Facebook and Blogger, but I
didn't seem to have problems connecting to many other sites..

But back to the topic, since there are many different VPN
technologies, it would take different methods to block each kind. 

IPSec type connections could be blocked just by blocking protocols 50 & 51.

They could block PPTP with blocking port 1723. L2TP over IPSec could
be blocked by its port, but it wouldn't work with 50 & 51 blocked
anyway.

Then they could do much more advanced tactits, like when Iran blocked
TOR by looking at the SSL certificates expiration dates, which the TOR
network had a pattern (that they've since worked around). That would
take some network processing power to look that deep into the
protocols..

Back to comp.security.misc | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

How to detect a VPN connection? Gilles <nospam@nospam.com> - 2011-10-07 01:21 +0200
  Re: How to detect a VPN connection? Barry Margolin <barmar@alum.mit.edu> - 2011-10-06 20:34 -0400
  Re: How to detect a VPN connection? Doug McIntyre <merlyn@geeks.org> - 2011-10-07 00:54 +0000
    Re: How to detect a VPN connection? Gilles <nospam@nospam.com> - 2011-10-07 12:08 +0200
      Re: How to detect a VPN connection? Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2011-10-07 10:43 +0000
        Re: How to detect a VPN connection? Gilles <nospam@nospam.com> - 2011-10-07 20:15 +0200
          Re: How to detect a VPN connection? Casper H.S. Dik <Casper.Dik@OrSPaMcle.COM> - 2011-10-07 22:39 +0000
            Re: How to detect a VPN connection? Gilles <nospam@nospam.com> - 2011-10-08 02:27 +0200

csiph-web