On January 25, the SQL Slammer worm almost completely blocked South Korea and caused problems around the world. The worm spread throughout the world in ten minutes. According to researchers at the University of California, it doubled every 8.5 seconds and its only limitation was the speed of Internet connection. SQL Slammer took advantage of an error of Microsoft's SQL Server 2000. The worm does not attack the hard disks, it only blocks the network.