Microsoft SQL Server is a database management system produced by Microsoft.
The codebase for Microsoft SQL Server originates in Sybase SQL Server.
A computer worm, named W32.SQLExp.Worm "SQL Hatter" which exploits a security vulnerability in this system was discovered in January 2003, and caused a large Internet slowdown on January 24.Possibly this worm caused the largest malfunction in Internet functionality since the infamous Internet Worm November 2, 1988.