I know MS says this is legit, but I received notification for windows security update on my Toshiba P55t-A118 touch screen which originally came with Win 8.1 and is currently running build 1607 of Win 10 pro. Boot up/login performance has been terrible since this update with 100% disk usage and no response so that I tried to bring up task manager and received "Preparing Security Options" prior to task manager appearing and being in a state of not-reponding. That now occurs every time I start or re-start the machine. 100% usage drops after about 20 seconds but still spikes under normal browsing.
I decided to uninstall that update but when I looked in the update history, it was not there. Instead I find it under installed programs which I thought was unusual. Anyone else had performance degraded after this update?
Am now doing a system restore prior to that update.