So yesterday i was on my computer andi got some screen that pops up when im online. The screen that poped up says that my computer is at risk and to run some virus scan on a program that doesnt exist on my computer. So i tried closing it but it will not close. I did scans with avast and can't find the issue with this, but i restart my computer and each time this thing pops right back up and i can close the program anyhow. I'm not sure what to do or what this is, anyone?