When your browser starts redirecting you to strange sites or you are inundated with pop-up ads, I’m sure your first thought is that you have a virus on your computer. It’s usually my first thought. In the past two months I’ve had two clients experiencing this behavior. In both cases I ran virus scans and malware scans and nothing turned up. More research was required.
What I turned up, although still rare, is a router hack. This is something that is very hard to protect against, maybe impossible for now, but what happens is that changes are made to your WiFi router to redirect your browser to sites you did not request. It is something that can be fixed but requires someone to examine the router and change settings.
If you suspect this problem there is an easy way to test. If your browser is redirecting you to strange sites, try another device like another computer or tablet in your home using your WiFi. Use the browser on that second device and see if the same thing happens. If so, it’s probably the router and not a virus on your computer.