What Is a BHO?A BHO, or browser helper object, is a component of Microsoft's Internet Explorer Web browser application. It is an add-in designed to provide or expand the functionality of the browser and allow developers to improve the Web browser with new features.
Why Are BHO's Bad?BHO's, in and of themselves, are not bad. But, like a lot of other features and functionality, if the BHO can be used to install additional features or functions that are useful, it can also be exploited to install features or functions that are malicious. Some applications, such as the Google or Yahoo toolbars, are examples of good BHO's. But, there are also many examples of BHO's which are used to hijack your Web browser home page, spy on your Internet activities and other malicious actions.
Identifying Bad BHO'sWith Windows XP SP2 (service pack 2) installed, you can view the BHO's that are currently installed in Internet Explorer by clicking on Tools, then Manage Add-Ons. Microsoft's anti-spyware utility, currently released as a Beta version, and some other tools such as BHODemon an be used to detect and remove malicious BHO's.
Protecting Your System From Bad BHO'sIf you are really concerned about bad BHO's and their affect on the overall security of your computer, you can just switch browsers. BHO's are unique to Microsoft's Internet Explorer and do not impact other Web browser applications such as Firefox.
If you wish to continue using Internet Explorer, but want to protect yourself from malicious BHO's, you can run BHODemon which has a real-time monitoring component, or an anti-spyware application that has a real-time monitoring component to actively detect and block bad BHO's. You can also periodically click on Tools, Manage Add-Ons to ensure no suspicious or malicious BHO's have been installed without your knowledge.