Firefox browser has been hijacked

Hi Everyone,

It seems my firefox browser has been hijacked as I have noticed that I can observe it going to different websites and even doing google searches.

Does this require me to reinstall my entire operating system? I’ve run a virus scanner before but it doesnt seem to function well. Also, I’ve done deletions on the machine to see if it would take care of things.
Virus scans would be my first step, however, I am running Ubuntu 12.04 which makes me worry that it has been hijacked. Random searches are taking place and websites pop up. I googled around and it seems like it would be a hacker. This only seems to happen with firefox.

Thanks very much.
S