Fileinfo Problem

Sounds like a rootkit virus. Quite hard to detect, and even harder to get rid of.

Is re-formatting and starting from scratch an option?

https://www.csoonline.com/article/3222066/malware/how-to-detect-and-remove-a-rootkit-in-windows-10.html

Rootkits can be a bugger to get rid of.

In future keep a complete backup of your hard drive and make sure it is only a week old. As soon as you get a problem, look at the latest files and keep them in a USB stick.
Now use the backup.
That's what I do.

I keep two backup hard drives because a virus can completely destroy 30 years of work.

Try running the Microsoft Safety Scanner. If the malware will not permit you to do so use this link.

What if the malware will allow him to do so? Would you recommend he doesn't use the link?

I concur with Solar E #3. Like you, a similar thing happened to me. My browser, Firefox, was high-jacked it seems, my searches were re-directed by, and to, a Russian search engine - names I typed myself, or clicked on, as well as any links in my emails., including links to help and support in my various apps. Not the least being impossible to repair or restore Windows 7 to an earlier working version.

I had to use my other PC to logon on to the internet to get help - nothing cured it - but by brute i got Firefox back by deleting every file with a Russian name, that without a Cyrillic keyboard to do a search, I had to list them to read them.

I sort of got it working, but so unstable, I decided to completely install Win 7 wiping out all my files in the process and then more problems because the updated programs emulating Windows 10 created a learning curve that is hard to climb.

I am not going to restore all my backup files from the BU drive. I will just pick out the ones I need at the time in case some are infected - albeit they have been cleared as virus-free by AVG by remote access to my PC.

But I suspect the 'virus' creates 'innocent' txt files with bits of data to collect for redirecting purposes - saved in ordinary Notepad files not suspect by AV apps.

Sorry for the negative - but it has all the hallmarks of ransom-ware - except nothing in my case has been received asking for payment to fix it. Meanwhile I think my email address has been hijacked and is being used for spamming.

Sorry for the delay getting back to this.

I have been off the grid for a while.Been working in my laboratory,which is air-gapped from outside world.

The solution was a complete system restore from an external 1 TB hard drive.

Still don't know what caused it,but at this point,it doesn't matter much.

Thanks for all the feedback guys!