Most of the infections that find there way into your computer can originate in the advertisements that show up in your web browser. Below is some information about what an Ad Blocker is and how it stops malware or viruses from infecting your computer
Great Article from CNBC on Malicous Ads Infecting your PC:
https://www.cnbc.com/2014/05/20/beware-of-malicious-ads-that-can-harm-computers-without-a-click.html