7. SQL Slammer – $750 Million
SQL Slammer successfully slowed down the worldwide Internet traffic on January 25, 2003. Within a few minutes after the initial attack, it infected nearly 75,000 machines. SQL Slammer wasn’t developed using SQL language, instead, it took advantage of a buffer overflow glitch that affected Microsoft SQL Server. Home PCs were largely unaffected by SQL Slammer unless they used MSDE. The worm is actually quite easy to remove because it is so small and doesn’t have any capability to write itself to a disk.