Here’s something that happens every day, a message appears in your web browser telling you a virus was found and to click OK to do a scan. To get straight to the point, this is a fake antivirus program designed to trick you into installing real malware.
If you see this on your browser, close the browser. Don’t click on any buttons. And most importantly, don’t panic. These scams are designed to scare you into making irrational decisions.
Below are screenshots of how it looks (click to enlarge the screenshots):
This type of scam happens on both Windows and Mac computers.