How can I prevent delta/conduit search from hijacking/changing my default search engine and homepage?
Also,Firefox now comes up with its native protection mechanism which doesn't allows any addon to make changes without user consent.
Strengthening User Control of Add-ons
see if spywareblaster can help
AntiToolbar helps warn and prevent the installation of toolbars: http://www.majorgeeks.com/files/details/antitoolbar.html. SuperAntiSpyware prevents browser hijacking: http://www.majorgeeks.com/files/details/superantispyware_free.html. WinPatrol can detect any system changes, and may help prevent any changes: http://winpatrol.com/.