A set of technologies developed by Microsoft Corporation that evolved from two other Microsoft technologies: OLE (Object Linking and Embedding) and COM (Component Object Model). ActiveX controls, widely written about, are among the many types of components to provide interoperability with other types of Component Object Model services.

Specifically, ActiveX controls provide a number of enhancements designed to not only aid in the distribution of components over networks but also to provide for the integration of controls into Web browsers. To control malicious code (such as viruses and worms), for example, ActiveX relies upon digital signatures and zones. That is, Microsoft browsers have been configured to allow ActiveX programs from servers in the trusted zone and to deny unsigned programs from servers in untrusted zones. Though the concept of trusted zones and digital signatures works well in theory, a variety of destructive worms in recent years (such as Melissa) that have worked their way through Microsoft Web browsers have shown that this theory has flaws.

See Also: Browser; Code or Source Code; Digital Signature; Malicious Code; Trust; Virus; Worm.