August 11, 2003: Blaster Worm (also known as Lovsan, Lovesan or MSBlast) is a computer worm that spread on computers running operating systems Windows XP and Windows 2000, during August 2003. The worm was first noticed and started spreading on August 11, 2003. The rate that it spread increased until the number of infections peaked on August 13, 2003. Once a network (such as a company or university) was infected, it spread quicker within the network because firewalls typically did not prevent internal machines from using a certain port. Filtering by ISPs and widespread publicity about the worm curbed the spread of Blaster.