# Stop user changing proxy settings on firefox Ubuntu

I currently use openDNS to filter user's web requests however they can often bypass this filtering by finding a proxy server (not yet on the openDNS block list) and configuring firefox to use it. Is there anyway I can just lock firefox so this non-admin user can't switch to a proxy full stop? or perhaps somehow stop them using a proxy with iptables..

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EDIT: Tested this on firefox 18. The *.js file name may be called all.js in older firefoxes. I'm not that familiar with firefox, that i could say if adding your own all.js would work too

create a text file containing :

//
lockPref("network.proxy.type", 1);
lockPref("network.proxy.http", "proxy.proxy.com")
lockPref("network.proxy.http_port", 8080)
lockPref("network.proxy.share_proxy_settings", true)
lockPref("network.proxy.no_proxies_on", "127.0.0.1,localhost")


The byteshift that file into mozilla.cfg with offset 13. Easiest is to use : http://www.alain.knaff.lu/howto/MozillaCustomization/cgi/byteshf.cgi

Then copy that mozilla.cfg into the directory where mozilla exe is located.

Then edit Mozilladir\defaults\pref\channel-pref.js

pref("general.config.filename", "mozilla.cfg");