Windows 8 is still supported with Microsoft Updates! Moreover had most severe problems with Update / Upgrade (of Windows 8 from DVD) from Windows Store to Windows 8.1 on one computer, other computer not, only difference Microsoft Account I was logged in with during Upgrade, the problem Windows 8.1 did not look like real Windows 8.1 and did not behave and work like real Windows 8.1.
Both computers (problems and no problems) where secured with Avast 2015 Internet Security (out-of-the-box default settings)
I tried once a suspicious pdf scan at virus total of 200 Mb => File was to big, these image “files” (Windows Explorer does not let you open the folder) are 30 Gb
Anyways you seem to be interested in these backup system images which maybe contain some latest and newest hack, probably a key logger virus (installer) that remains even after a rebuild OS, we can DM Twitter chat about it at @art_rotterdam, just follow me and send notification for DM