Browser Hijack Blaster runs in the background, constantly watching for attempts to alter various Internet Explorer settings, and for newly added BHOs (Browser Help Objects). If an attempt is detected, you are notified immediately, and presented with details on the attempt, plus the option to either allow the change, or revert to the previous value.
With Browser Hijack Blaster, you will be notified if an ActiveX control tries to silently install a new BHO (Browser Help Object) - and you will be presented with the ability to remove that BHO or allow it.