index.html.bak.bak

I have this issue that started a few days ago: my "index.html" page changes to "index.html.bak.bak" while on the server. I use Dreamweaver CS3 for this particular site, but I also have Dreamweaver 2017 (I prefer to use the CS3 version- been using it for years and can't let go

The changing of the index happens after I upload it to the server- usually about several hours later (even my computer is off- so can't imagine I'm "sleep typing"). I've been running this news site for years, and have my set way of updating it and uploading. Never had an issue until Monday. I then would delete this newly created "index.html.bak.bak" and replace it with my undamaged "index.html"

What appears on the homepage is the basic layout with images/graphic, but all in gibberish. The site is in Russian and none of the other pages deal with this issue on the site. I was using Windows Cyrillic encoding, but changed to Unicode. I don't know if this will fix it, but I would like to be prepared if/when it happens again. Could it possibly be a virus?

Thanks in advance for any help/suggestions!