Ok in another thread on this a user 4 days ago followed this advice of mine to uninstall McAfee and reinstall it
"Uninstall via windows Programs and features then run MCPR
Download the MCPR tool.
Reboot and follow the preparation steps for an install.
That said this gives the new 16.0.R6 version but we are surprised everything is working fine now. has any1 reinstalled clearing the old install with the removal tool and cleaning up prior to the install?
In that thread only 1 tried this any1 here interested
Ok, tried it today. Removed all potential s/w threads using the tools as given above, checked every possible issues and then reinstall the latest McAfee Total Protection as given in the procedure. Then rebooted the laptop and guess what : same issue as highlighted in this forum. McAfee running as high as 94%. Bad luck but it does not work on my Acer laptop. I then used my option of starting the laptop but login-in after ±20mn, and as before I am then able to use it as normal.
I'm having a similar problem with MMSSHOST.EXE, except mine is using 100% of my disk I/O for a REALLY long period at startup (Tens of minutes). Over a billion I/O read bytes and it's many times more than the next closest process (distant second place is System). I do have a NVIDIA graphics card. A GTX970. Eventually it will settle down, but it takes a long time and my PC is almost unusable until it does.
I am experiencing a similar problem. MMSSHOST.exe is using 98% CPU. I have McAfee on two of my laptop and one desktop. Only one laptop has this problem. This one is ASUS X550LA; OS: Windows 10 Home x64. Actually I once solved this problem by reinstall McAfee a couple days ago. It works well for like three or four days after reinstall but now the problem comes back.
I think I am going to uninstall for now and wait for the update that can solve it.
Thanks for reporting this now 9 users . If you are able put your hand up to assist McAfee support staff in getting logs so they can fix the issue. They have not seen it happen on their Pcs nor have we mods seen it.