From: lew.pitcher@digitalfreehold.ca
On Sunday December 20 2015 12:56, in
comp.protocols.tcp-ip, "bit-naughty@hotmail.com"
wrote:
> OK, so I had an experience with censorship - someone was trying to go to a
> particular porn site, and it said "The governent has blocked this page" or
> whatever. I'd like to know how this is pulled off - the router in the middle
> didn't only block the HTTP request, but also - *answered* it, saying that
> the site was blocked!! I thought routers were low level TCP/IP beasts, how
> are they answering HTTP requests? Or am I barking up the wrong tree? Did it
> get the text "The government" blah blah from a _server_ somewhere? How?
There are all sorts of ways. Here are a few:
A1) "The government" "confiscates" the porn site's domain name, and
substitutes their own, captive, IP address. User's web browser
requests 'porn.porn', and gets a government website that provides
the "blocked" notice. This is how the FBI (for instance) "confiscates"
websites.
A2) The user's DNS provider lies (for whatever reason) and substitutes their
own, captive, IP address. User's web browser requests 'porn.porn', and gets
an ISP website that provides the "blocked" notice.
B) The user's ISP implements a proxy web server and directs the user's HTTP
requests to/through it. The proxy web server detects a request for a "banned"
site, intercepts it and replies to the user with a canned "blocked" webpage.
C) Some network provider along the route performs "deep packet inspection",
and intercepts requests to a "banned" site. Instead of passing those packets
along the network, the network provider responds in kind with a
canned "blocked" webpage.
--
Lew Pitcher
"In Skills, We Trust"
PGP public key available upon request
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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