Definition:
ActiveX controls are the modern rendition of OLE, or .OCX files. A simplistic example of OLE (Object Linking and Embedding) allows a user to embed the calculator into a word processor. ActiveX controls rely on the Windows operating system, requiring developers to create version specific controls. Unlike Sun's Java, ActiveX is able to interact with the operating system.
The Kak worm is perhaps the most notorious malware to exploit vulnerabilities in ActiveX. Kak is a worm that spread simply by reading email - or even just displaying email in the preview pane - in Microsoft Outlook and Outlook Express. The Kak worm took advantage of a security vulnerability in two ActiveX controls, scriptlet.typelib and Eyedog.
