Browser Helper Object: Difference between revisions

Each time a new instance of Internet Explorer starts, it checks the [[Windows Registry]] for the key ''HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects''. If Internet Explorer finds this key in the registry, it looks for a [[Universally unique identifier#In COM|CLSID]] key listed below the key. The CLSID keys under Browser Helper Objects tell the browser which BHOs to load. Removing the registry key prevents the BHO from being loaded. For each CLSID that is listed below the BHO key, Internet Explorer calls CoCreateInstance to start the instance of the BHO in the same process space as the browser. If the BHO is started and implements the IObjectWithSite interface, it can control and receive events from Internet Explorer. BHOs can be created in any language that supports [[Component Object Model|COM]].<ref>Roberts Scott, ''Programming Microsoft Internet Explorer 5'', Microsoft Press, 1999, {{ISBN|0-7356-0781-8}}</ref>

 

== Concerns ==

The BHO [[application programming interface|API]] exposes [[hooking|hook]]s that allow the BHO to access the [[Document Object Model]] (DOM) of the current page and to control navigation. Because BHOs have unrestricted access to the Internet Explorer event model, some forms of [[malware]] have also been created as BHOs.<ref>{{Cite web|title=Browser Hijack Objects (BHOs)|url=https://blog.malwarebytes.com/threats/browser-hijack-objects-bhos/|access-date=2021-12-05|website=Malwarebytes Labs|language=en-US}}</ref>