[Gllug] how to check for a transparent proxy

[Xander D Harkness]

Mark Lowes wrote:
> On Sun, 2002-12-01 at 03:42, Xander D Harkness wrote:
> 
>>I am told by my connectivity provider that port 80 traffic is not 
>>filtered or cached.  I pay for a clean business connection and I would 
>>expect it not to be cached / cached.
>>
>>If I browse to amazon.com or amazon.co.uk all of the links to the images 
>>are broken.  For a long time I thought it was amazon.
> 
> 
> telnet <IP you know isn't running anything on port 80> 80
> 
> if you get connection refused then there's no proxy, if you get a
> session then you're hitting a proxy.
> 
So, it looks like it is a local problem.

######################################

I grabbed some of the access log from squid:

TCP_MISS/503 1609 GET 
http://images-eu.amazon.com/images/P/1855496771.02.TZZZZZZZ.jpg - NONE/- 
text/html

##################################

If I put this URL in a browser I get:

#####################################

The following error was encountered:

     Unable to determine IP address from host name for images-eu.amazon.com

The dnsserver returned:

     Name Error: The domain name does not exist.

####################################

So I ran a few dns checks

#####################################

dig amazon.com

no IP given

dig www.amazon.com

207.171.183.16

dig images-eu.amazon.com

CNAME   images-eu.amazon.speedera.net.

######################################

Now this starts to look interesting.  Over the last year I have had a 
lot of pop-ups, pop-unders, spam and many other annoyances from speedera 
so in my nameservers I put an a record for speedera pointing to a good 
IP which would server a blank page of html.  (pointing to 127.0.0.1 
causes most browsers to give a pop-up error message)

Aside from the errors in Amazon all has been well and all who use the 
proxies and dns servers have been happy.

I guess a better answer is to put speedera in the proxy ban file and the 
mail rbl list :-)

Thanks for all the suggestions.

I am happy that I know know a number of methods to check for a 
transparent proxy and have solved my hiccough.

Kind regards
Xander





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