SQL Slammer, also known as Sapphire, is the fastest-spreading computer worm in recorded history. Launched at 05:30 UTC on January 25, 2003, the 376-byte worm doubled the number of infected hosts every 8.5 seconds and infected approximately 75,000 vulnerable SQL Server hosts within 10 minutes. At its peak it was sending 55 million UDP packets per second. The worm’s speed caused severe collateral damage: 27 million South Korean internet users and all South Korean mobile phone service was knocked offline; Bank of America’s 13,000 ATM machines stopped working; five of the thirteen DNS root servers experienced degraded performance; Continental Airlines cancelled or delayed flights due to disrupted check-in systems; 911 emergency dispatch in Bellevue, Washington lost computer-aided dispatch. The worm was purely a denial-of-service and propagation payload with no data theft component — but the bandwidth consumption alone caused widespread internet disruption. The security patch (MS02-039) had been available for 6 months. SQL Slammer demonstrated the catastrophic potential of compact, high-speed network worms targeting widely deployed database infrastructure.