Windows 10 MsMpEng running all my apps at once on boot

[ontodva]

Since installing the Windows 10 Anniversary update, booting has been slow and the PC is sluggish for a while. As soon as I could get Task Manager open I saw C: had 100% utilisation. I ran Resource Monitor and saw that MsMpEng apparently had a long list of my installed programs running at the same time. Each was reading roughly 60KB a second. This lasted a minute or so. What's going on?

 

[Neemobeer]

MsMpEng is the Windows Defender service. With the anniversary updates comes cloud analytics to Windows Defender. It may be building a baseline for your system. How long have you had the update installed?