A computer worm that infected over ten million Windows personal computers on and after 5 May 2000, when it started spreading as an email message with the subject line “ILOVEYOU” and the attachment “LOVE-LETTER-FOR-YOU.TXT.vbs.”
On the machine system level, ILOVEYOU relied on the scripting engine system setting (which runs scripting language files such as .vbs files) being enabled, and took advantage of a feature in Windows that hid file extensions by default. In other words, Windows would parse file names from right to left, stopping at the first period character, showing only those elements to the left of this. As the latter file extension “vbs” was hidden, the attachment, could thus display the inner fake “TXT” file extension, leading unwitting users to think it was a normal text file - normal text files being considered to be innocuous as they are incapable of running executable code. Because the malware 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.
Opening the attachment activated the Visual Basic script (“vbs”) and inflicted damage on the local machine, overwriting random types of files (including Office files, image files, and audio files). It then sent 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.
ILOVEYOU was created by Onel de Guzman, a college student in Manila, Philippines, who was 24 years old at the time. De Guzman, who was poor and struggling to pay for Internet access at the time, created the computer worm intending to steal other users’ passwords, which he could use to log in to their Internet accounts without needing to pay for the service. The message was generated on May 4, 2000 and began to spread across the world westward, following daybreak, as employees began their workday. It first reached Hong Kong, then Europe, and finally the United States in a day, through corporate email systems. 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. The outbreak was later estimated to have caused US$5.5–8.7 billion in damages worldwide, and estimated to cost US$10–15 billion to remove the worm. 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. At the time and still today, ILOVEYOU is considered one of the world’s most virulent computer virus in history.