ILOVEYOU was a computer worm that first appeared on May 5, 2000. The worm was sent by email using the subject "ILOVEYOU", with the worm attached. The worm would look like a text file, until it was opened. The file would be called "LOVE-LETTER-FOR-YOU.txt.vbs". Because of Microsoft Windows' default options, the user would not see the ".vbs" extension, and mistake it for a harmless text file which cannot execute code.