On August 11, 2003, the Blaster worm was launched to exploit a vulnerability in a number of Microsoft Windows operating systems. When successfully executed, it caused the operating system to fail. Although the security community had received advisories from CERT/CC and other organizations to patch this critical vulnerability, Blaster reportedly infected more than 120,000 unpatched computers in the first 36 hours.
By the following day, reports began to state that many users were experiencing slowness and disruptions to their Internet service, such as the need to frequently reboot. The Maryland Motor Vehicle Administration was forced to shut down, and systems in both national and international arenas were also affected.
Experts consider Blaster, which affected a range of systems, to be one of the worst exploits of 2003. Microsoft reported that that at least 8 million Windows computers were infected by the Blaster worm.
On August 29, 2003, Jeffrey Lee Parson, an 18-year-old from Hopkins, Minnesota was arrested for creating the B variant of the Blaster worm; he admitted responsibility and was sentenced to an 18-month prison term in January 2005.