Blacklists and inaccessible URLs

[David Bandel]

On Sun, 20 Feb 2005 11:57:35 +0800, Chong Yu Meng
<chongym at cymulacrum.net> wrote:
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> Hi All,
> 
> I've got a rather strange problem for which I need to provide some
> proof. There is a particular website that is inaccessible to all but a
> few people locally, but anyone who tries to connect to it from an
> overseas location is able to see it.
> 
> I believe that either :
> 1. the web administrator has a blacklist of IP addresses that drops
> connections from everyone except a few authorized people
> 2. the firewall is configured to accept connections from only a few
> authorized hosts.

It's possible their firewall is one of the borken ones that don't
accept packets with the ECN (expect congestion notification) bit set. 
iptables can help identify and mangle your packets to turn off ECN to
those sites.

> 
> Short of calling the web administrator (who may not entertain my
> enquiries or may report me as a suspected hacker), is there a way for me
> to find out, or prove that this is the case?

You're getting paranoid here.  Whether you're a cracker or not is the
webmasters problem, not yours.

Take a Linux box with ECN support compiled in.  Make sure it's turned
off and try to get to the site.   If that works, turn ECN on and see
if you're blocked.

You can also use tcptraceroute (which by default uses port 80) to
trace to the site.  Just apt-get install tcptraceroute in Debian or
variants.  In RPM distros, check rpm.net to see of they have a copy
for your distro.

> 
> Thanks in advance!

Ciao,

David A. Bandel
-- 
Focus on the dream, not the competition.
            - Nemesis Air Racing Team motto