It's Avast's NG feature preparing itself. This happens when you first reboot computer after Avast 2015 installation. This preparing SHOULD take few minutes, but many people have had problems with this process taking hours and many other problems too, like this preparing happening after
every computer reboot, even it should only happen once. I had this "after every reboot" problem, which forced me to disable the NG component.
So, mfutil is one of processes which is launch in this preparing process. And this process is CPU consuming.
Here's one reference link:
https://forum.avast.com/index.php?topic=157998.0