Not sure what's it's called either but seems like my Note 5 has this issue too. I'll get a banner type pop up or adware of sorts, there will be a x in the top right corner and bottom right corner says o.o out.
If I click on it it gives you two options, downloading and app to remove or it says a manual removal option which asks for like your EMI or phone serial number or something. I've noticed it like the last month or so, and have Malwarebytes installed.
Not sure what's causing it or where it came from, but it's really annoying. Sounds like the OP has something like I have.