Rootkit detection

I have gotten what I think is a root kit on my Mozilla Firefox installation. It is 'search:conduit' I have tried to delete this nusance but, it persists to haunt me. I am running Norton Antivirus vers.19.9.9.0.9. Is there a Norton product that would have caught this intrusion and  deleted it? I have tried all kind of rootkills; but, none have found it.  Do you have any advise on removing this?

Thanks,

Joe