I was researching a topic and was caution to avoid questionable sites. Suddenly, on my screen, there was a pop up box appearing to be from Norton, that I have 5 virus on the computer. I thought it was probably phishing, so I used arrows to get out. I ran Norton in quick and full and nothing, it says my computer is fine. My question- How did I get this on my screen when I when I have protection. Is my computer really OK? Thanks