I posted this in case any forum members had a similar experience, though I couldn't find it referred to specifically on the DC Forum.
I clicked on a file the other day and this popped up on my laptop screen:
I did a DuckGo
search on "Filefacts.net - Smart File Advisor"
, and it is apparently benign software, being a "FREE" offering from various download sites of mixed reputation. Looks like a PUP (Potentially Unwanted Program), though neither MS Security Essentials (Defender) nor Malwarebytes objected to it.
I have no idea how this thing got installed on my system. I presume it must have slipped past me or was silently installed when I was hurriedly clicking "Next" whilst installing some program or other that I had downloaded and wanted to trial.
Anyway, I detached from the Internet and uninstalled the software using RevoUninstaller on max level scrubbing.
The last thing I want is some third-party software insinuating itself in unsolicited fashion into my system and "helpfully" intercepting system calls.
It could have been as bad as Norton/Symantec AV...