A BHO is a small program that runs automatically every time you start your Internet browser. Normally a BHO is installed on your system by another software program eg; Go!Zilla, this downloading utility, installs a BHO created by Radiate (formerly Aureate Media); the BHO component tracks which advertisements you see as you surf the Web.

So what do BHOs do? The answer is literally "anything" - but in general they will have something to do with 'helping' you browse the Internet. Sadly many of them fall into the "ad-ware" or "spyware" category:- in that they are installed without your knowledge and they monitor the websites you visit and report this data back to their creators.