Explorer.Zip Worm

Unleashed in 1999, the  Explorer.zip worm followed in the footsteps of the Melissa Virus by spreading via e-mails that appeared to be from someone the recipient knew. Emails carried the worm as a file attachment that, once activated, displayed a fake error message to the user, whilst randomly altering certain file types and even deleting Microsoft Word, Excel, and PowerPoint files.

Unlike Melissa which gathered e-mail addresses from Outlook, Explorer instead monitored the inbox of the infected computer and spread itself by sending automatic replies to senders, using the same email subject line as the original message.