A small program that runs automatically every time you start your Internet browser. Usually, a BHO is installed on your system by another software program. Some BHO's are malicious spyware components which attach themselves limpet-like to Microsoft's Internet Explorer and act as a toolbar or other browser plug-in that is hard to remove ( uninstall). The worst of these can radically change browser settings, including home pages and bookmarks, and make it difficult or impossible for people to change settings back, without their knowing how to manipulate the Windows Registry. See also: Spyware & Adware Removal Blocking BHOs in Internet Explorer

A component that Internet Explorer will load whenever it starts, shares IE's memory context, can perform any action on the available windows and modules. A BHO can detect events, create windows to display additional information on a viewed page, monitor messages and actions. There are many exploits of this technology which search all pages you view in IE and replace banner advertisements with other ads, monitor and report on your actions, change your home page, etc.

a COM object that is instantiated for every Internet Explorer browser window

see “Browser Plug-in.

a small program that is installed on your PC and runs within your browser

a small piece of