ILOVEYOU

ILOVEYOU, sometimes referred to as Love Bug or Love Letter, is a computer worm that attacked tens of millions of Windows personal computers on and after 5 May 2000 local time in the Philippines when it started spreading as an email message with the subject line "ILOVEYOU" and the attachment "LOVE-LETTER-FOR-YOU.txt.vbs".

The latter file extension ('vbs', a type of interpreted file) was most often hidden by default on Windows computers of the time (as it is an extension for a file type that is known by Windows), leading unwitting users to think it was a normal text file. 

Opening the attachment activates the Visual Basic script. The worm inflicts damage on the local machine, overwriting random types of files (including Office files, image files, and audio files; however after overwriting MP3 files the virus hides the file), and sends a copy of itself to all addresses in the Windows Address Book used by Microsoft Outlook. This made it spread much faster than any other previous email worm.

Messages generated in the Philippines began to spread westwards through corporate email systems. Because the worm used mailing lists as its source of targets, the messages often appeared to come from acquaintances and were therefore often regarded as "safe" by their victims, providing further incentive to open them. Only a few users at each site had to access the attachment to generate millions more messages that crippled mail systems and overwrote millions of files on computers in each successive network.

The worm originated in the Pandacan neighborhood of Manila in the Philippines on May 5, 2000, thereafter following daybreak westward across the world as employees began their workday that Friday morning, moving first to Hong Kong, then to Europe, and finally the United States. 

The outbreak was later estimated to have caused US$5.5–8.7 billion in damages worldwide, better source needed] and estimated to cost US$15 billion to remove the worm. Within ten days, over fifty million infections had been reported, and it is estimated that 10% of internet-connected computers in the world had been affected. Damage cited was mostly the time and effort spent getting rid of the infection and recovering files from backups. To protect themselves, The Pentagon, CIA, the British Parliament and most large corporations decided to completely shut down their mail systems.

The ILOVEYOU worm infected computers all over the world. At the time it was one of the world's most destructive computer related disasters ever.