Microsoft has just confirmed that their recent update (KB 3004394) is causing a range of serious problems and recommends removing it.
Users are reporting that USB 3.0 drivers are broken, User Account Control (UAC) prompts are behaving oddly and the Windows Defender anti-malware service has been disabled by the update. Microsoft has acknowledged that it even prevents the installation of future Windows Updates.
Note that the problems with this patch only apply to Windows 7, so if you have been diligent in paying your Microsoft tax, you're safe. If insist on staying with an old OS, and have Windows 7 set to automatically update every Tuesday, you should consider permanently disabling that feature.
http://www.forbes.com/sites/jasonevangelho/2014/12/13/new-windows-7-patch-is-effectively-malware-disables-graphics-driver-updates-and-windows-defender/
(Score: 2) by jmorris on Monday December 15 2014, @07:52PM
Then their update model is fundamentally broken.
Reread what I wrote. Where do you think Microsoft would have got their samples? Random eBay vendors or direct from the vendor? It was only the counterfeit chips that were being destroyed and Microsoft truly had no way to know until customers (Microsoft's customers) started complaining, at which point they did the right thing.