Virus Message Every Time Scheduled Cloud Backup Begins

At first I thought this was related to a web site I was on, but now I see that every time Acronis begins its scheduled weekly backup (which will apparently take 3 months BTW - I've given up and done a backup to HD), I start getting virus alerts, and Acronis backup failure notices immediately afterwards. Last week it was Ransom/Reveton, this week it's W97M/Donoff. I was doing absolutely nothing this week.

Since I update my HOSTS file with the most recent ones from winhelp2002, run adblocker etc., I know nothing is getting through on the few sites I go to - and I think Amazon.com is pretty safe.

I've NEVER had a virus until I started using Acronis - this is since my first PC in 1982.

What gives?