The WDEF virus was discovered simultaneously in Belgium and the United States. It reproduces itself in the “Desktop” file by copying a WDEF resource, and is transmitted by simply inserting an infected disk into the Macintosh. It can affect the normal operation of the Macintosh — a special variant also emits beeps — but it does not specifically alter data. The System file, as well as some applications, may contain a WDEF resource without being infected.
The Rival WDEF vaccine also recognizes WDEF variants.