Disclaimer: These steps may do produce undesiderable behavior in your browser, these are notes i have written for myself and am sharing to help anybody that could benefit from them.
How to stop Firefox from automatically making connections without my permission
1) Clean all the live bookmarks if any.
2) Disable auto update (Edit -> Preferences -> Update ->
Never check for updates (not recommended: security risk)
and uncheck Update Search Engines)
3) Disable auto update for plugins (Tools -> AddOns -> Extensions
At the top of the tab, click the Tools for All Add-ons menu and uncheck Update Add-ons Automatically, then select Reset All Add-ons to Update Automatically.)
4) Anti-phishing list updating (Edit -> Preferences -> Security ->
Block reported web forgeries. and
Block reported attack sites)
5) Add-on blocklist updating, Add-on metadata updating, Link prefetching
In the location bar write: about:config and set:
extensions.blocklist.enabled -> false
extensions.getAddons.cache.enabled -> false
network.prefetch-next -> false