ActiveX controls are available as free downloads on Internet Explorer. When you visit a website that contains an ActiveX control, the browser asks you if you want to install it.
ActiveX controls are small add-on programs that allow animation in Web browsers, enable you to view a website, or help with common tasks on Internet Explorer and application programs in Windows and Macintosh. They are specific to the version of Internet Explorer in use. Common examples are the controls for Flash Player, Shockwave, Microsoft Silverlight and Windows Media Player. Some are pre-installed to improve the browsing experience.
Not all controls are necessary or desirable; some have security holes and some are capable of phishing for personal information, displaying pop-up ads, and even infecting a computer with viruses. Internet Explorer provides as many details as possible about the website and the control publisher for you to verify the content as trustworthy before choosing to install a given control. The browser automatically blocks content from unverified publishers. Additionally, Microsoft periodically releases Windows updates with "killbits," features that block specific unsecure controls.
You can view any ActiveX controls you already have by clicking the Tools button and selecting Manage Add-ons. Internet Explorer allows you to block or allow ActiveX controls, while modern versions 9 and later contain features like control filtering, whitelisting trustworthy websites, and Protected Mode.