On Sat, 2011-04-02 at 12:15 +0530, Partha Chowdhury wrote: > My ISP is running a transparent proxy server on port 80 as I found out > from this thread > > http://mailman.archlinux.org/pipermail/arch-general/2011-March/019172.html > > Now from last two or three days, I keep getting pop-up ads from a > particular domain on every website i go to - even on text only websites > ! If i choose another proxy server in firefox , then that does not > appear on any site. But i normally connect to internet, that specific > pop-up to a very particular website appears on every single page. If I > install adblock plus in firefox, then of course no ads are displayed. > > So is it possible that my ISP is serving that ad by intercepting > incoming http traffic ? Yes, proxyservers can intercept pages and modify them. I used to have a transparent squid proxy that would filter ads and replace them with a 1x1px transparent pixel. If you're paying for this internet line, I would suggest to switch to a different provider. Inserting ads in HTTP pages for a connection that is being payed for is not-done.