Several notable security flaws have been found in Windows 2000. Code Red and Code Red II were famous computer worms that used problems with indexing service of Windows 2000's Internet Information Services (IIS) to caused a security problem. In August 2003, two major worms named the Sobig worm and the Blaster worm began to attack millions of Microsoft Windows computers and caused many problems for system administrators and computer operators who used Windows 2000. This was very embarrassing for Microsoft, and caused many corporations and governments to look carefully at Microsoft's security problems.