Q: Getting pop up ads

I am job searching and I signed up with a couple of job sites. Suddenly, I'm getting a lot of pop up ads, even from irrelevant sites. I'm also getting spam pop up ads telling me I "may" have a virus and once these ads appear, I can't get rid of them no matter how many time I click on the "leave page" button. What should I do? I called Mac Support and they told me to clear out my cache, history and cookies, but I'm still getting these pop ups.