What is a Browser Helper Object? A Browser Helper Object, often referred to as a "BHO", is a code module that is loaded into Exporer and Internet Explorer by Windows. Browser Helper Objects were designed to allow developers to extend the functionality of Windows.
While there are many useful browser extensions, there are also extensions developed by Spyware/Adware authors designed to "spy" on your surfing habits.
Where are they stored? Browser Helper Objects can be stored anywhere on your hard drive. Legitimate applications most often store them with the main application so they can be easily identified. Browser Helper Objects typically have the file extension of .DLL, but can have any extension.