Believe it or not, some of your operating systems and computers have little built in firewalls. They're not much, but they block a lot more than you think. Windows Defender is a great example of this. Viruses can infect your computer in almost every way possible. Hell, just watching videos on Youtube could give you a virus. This site is so full of different ads and generated pictures it's almost impossible to find and isolate the one with the virus. There's even a chance they all have different viruses, you never know. Some are not detected at first because they work as a "worm" and slowly infect your computer little by little. I think the best solution would be to clear as many ads as you can, and also update your virus protection. Although it is not cheap, Norton Antivirus is the #1 best out there folks. Scans incoming and outgoing files on your computer. Well good luck anyways!