Editing Windows Update (section)

===Critical Update Notification Utility===
[[File:Windows 98 - Critical Update Notification.png|thumb|Screenshot of the Critical Update Notification [[dialog box]] in [[Windows 98]]|alt=]]
''Critical Update Notification Utility'' (initially ''Critical Update Notification Tool'') is a [[background process]] that checks the Windows Update website on a regular schedule for new updates that have been marked as "Critical." It was released shortly after Windows 98.

By default, this check occurs every five minutes, plus when Internet Explorer starts; however, the user could configure the next check to occur only at certain times of the day or on certain days of the week. The tool queries the Microsoft server for a file called "<code>cucif.cab</code>", which contained<!--Not anymore--> a list of all the critical updates released for the operating system. The tool then compares this list with the list of installed updates on its machine and displays an update availability notification. Once the check is executed, any custom schedule defined by the user is reverted to the default. Microsoft stated that this ensures that users receive notification of critical updates in a timely manner.<ref name="cun-kb">{{Cite web |url=https://support.microsoft.com/en-us/help/224420/description-of-the-windows-critical-update-notification-utility |title=Description of the Windows Critical Update Notification utility |date=5 December 2007 |website=Support |publisher=[[Microsoft]] |access-date=22 November 2018 |archive-date=26 July 2020 |archive-url=https://web.archive.org/web/20200726012559/https://support.microsoft.com/en-us/help/224420/description-of-the-windows-critical-update-notification-utility |url-status=live }}</ref>

An analysis done by security researcher [[H. D. Moore]] in early 1999 was critical of this approach, describing it as "horribly inefficient" and susceptible to attacks. In a posting to [[BugTraq]], he explained that, "every single Windows 98 computer that wishes to get an update has to rely on a single host for the security. If that one server got compromised one day, or an attacker cracked the [Microsoft] DNS server again, there could be millions of users installing [[trojan horse (computing)|trojans]] every hour. The scope of this attack is big enough to attract crackers who actually know what they are doing..."<ref>{{Cite web |url=http://seclists.org/bugtraq/1999/Jan/0400.html |title=How the MS Critical Update Notification works... |last=Moore |first=H. D. |date=29 January 1999 |website=BugTraq mailing list archive |via=seclists.org |access-date=30 July 2008 |archive-date=21 June 2009 |archive-url=https://web.archive.org/web/20090621010729/http://seclists.org/bugtraq/1999/Jan/0400.html |url-status=live }}</ref>

Microsoft continued to promote the tool through 1999 and the first half of 2000. Initial releases of [[Windows 2000]] shipped with the tool. The tool did not support Windows 95 and Windows NT 4.0.