The ILOVEYOU Virus
The email you absolutely should not have opened. On May 4, 2000, an email landed in inboxes worldwide with the subject line "ILOVEYOU" and an attachment promising a love letter — then it quietly sent itself to everyone in your address book and overwrote your files. Within ten days, tens of millions of computers were infected, and the damage estimates eventually climbed toward $10 billion. It was the moment the internet learned not to trust attachments.