Microsoft has reported a critical flaw in Internet Security and Acceleration Server 2000. The problem lies with the vulnerability in the H.323 protocol. If exploited successfully, hackers can gain control of the vulnerable system.
Affected software:
Microsoft Internet Security and Acceleration Server 2000
Microsoft Small Business Server 2000 (which includes Microsoft Internet Security and Acceleration Server 2000)
Microsoft Small Business Server 2003 (which includes Microsoft Internet Security and Acceleration Server 2000)
Read the bulletin at http://www.microsoft.com/technet/treeview/?url=/technet/security/bulletin/MS04-001.asp