It's not a virus, which is why anti-virus apps aren't working. It looks like adware to me, most likely built into one of your free apps. You can try an ad blocker to see if that works, but otherwise you'll have to remove and any apps you have one at a time and use the phone a bit to see which one is causing it. Some apps are more prone to it than others, such as pirated apps, gambling apps, "adult" apps, and pretty much anything else not found in the Play store. So I'd start eliminating those first if you have any of them (and pirated apps are frowned upon in general).
You may also want to try booting into safe mode first to see if it goes away. It should, but some of the dirt cheap, no name manufacturers put ads into the OS itself. If you run it in safe mode and the ad still pops up, then there's nothing you can do besides switching to one of the name brand phones.
12-12-2018 01:58 PM