#3. ILOVEYOU ($15 Billion)
In 2000, ILOVEYOU, also known as the “Love Bug,” exploited human nature by disguising itself as a love letter and tricking recipients into opening it. It was only a matter of hours before computer systems across the world were tied up by this virus. It has stunned experts with its fast and wide reach. Similar to the Melissa Worm in 1999, ILOVEYOU spread via e-mail with the subject line I Love You, and when the user opened the attached file, it sent copies of itself to the user’s entire address book. It would look for attachment extensions like .jpeg, .mp3, .css and .hta, overwriting these with its own form and changing the extension to .vbs or .vbe. This virus affected companies as well as individuals, including the Dow Jones Newswires and the Asian Wall Street Journal. Companies had to close down e-mail systems to help stop the spread. In Australia, a reported 80% of the companies were hit.