How to Lock Firefox Proxy Settings

1. Create a file called loadcustom.js in /usr/lib/firefox-3.0.x/defaults/preferences/,
where 3.0.x will be something like 3.0.11 or 3.0.14 depending on your current version.

Put the following in /usr/lib/firefox-3.0.x/defaults/preferences/loadcustom.js

// tell firefox to load customized config file
pref(“general.config.obscure_value”, 0);
pref(“general.config.filename”, “firefox.cfg”);

2. Create a file called firefox.cfg in /usr/lib/firefox-3.0.x/ with the following content
(the first line in both files must start with a comment):

// Lock specific preferences in Firefox so that users cannot edit them
lockPref(“app.update.enabled”, false);
lockPref(“network.proxy.http”, “”);
lockPref(“network.proxy.http_port”, 8080);
lockPref(“network.proxy.type”, 1);
lockPref(“network.proxy.no_proxies_on”, “localhost,,”);
lockPref(“network.proxy.share_proxy_settings”, true);
lockPref(“browser.startup.homepage”, “”);

3. Restart Firefox, and the preferences should be locked down.
You should be able to use this to lock down any setting in about:config.

Thank you

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