Slammer worm

On January 25, 2003, the Slammer worm triggered a global Internet slowdown and caused considerable harm through network outages and other unforeseen consequences. The worm reportedly shut down a 911 emergency call center, canceled airline flights, and caused automated teller machine (ATM) failures.

According to media reports, First USA Inc., an Internet service provider, experienced network performance problems after an attack by the Slammer worm, due to a failure to patch three of its systems. Additionally, the Nuclear Regulatory Commission reported that the Slammer worm also infected a nuclear power plant’s network, resulting in the inability of the computers to communicate with each other, disrupting two important systems at the facility.

In July 2002, Microsoft had released a patch for its software vulnerability that was exploited by the Slammer worm. Nevertheless, according to media reports, some of Microsoft’s own systems were infected by the Slammer worm.