Initial releases of Windows 2000 shipped with the tool, but Windows 95 and Windows NT 4.0 were not supported.It was superseded by Automatic Updates in Windows Me and Windows 2000 SP3.Fixes to Windows 98 to resolve the Year 2000 problem were distributed using Windows Update in December 1998.
It also narrowed down the list of available updates for the operating system and related components by sending details of what operating system version, service pack, and locale are installed.
German technology web site published an analysis of the Windows Update communication protocol in February 2003, which received wide attention on technology web sites.
Instead of the five-minute schedule used by its predecessor, the Automatic Updates client checks the Windows Update servers once a day.
The user is given the option to download available updates then prompt the user to install them, or to notify the user prior to downloading any available updates.
If that one server got compromised one day, or an attacker cracks the MS DNS server again, there could be millions of users installing trojans every hour.