How do I stop virus invasion: your-mac-security-analysis[.]net

Suddenly, a loud beep and this page that looks like online apple support pops up and warns me that my computer is infected with three viruses. Google search <How to get rid of Your-mac-security-analysis.net POP-UP Scam (Mac) - virus removal guide.webarchive> "Your-mac-security-analysis[.]net is an untrustworthy, deceptive website which is designed to trick people into installing a questionable app called Cleanup My Mac. To trick them into it, your-mac-security-analysis[.]net displays a fake message/notification saying that visitor's computer is infected with viruses and offers to remove them with the aforementioned app. We advise not to download (and install) apps that are promoted through deceptive pages. It is possible that some of them may be used to trick people into installing malware." I tried all the folder: /Library/Launch etches and it still pops up and takes over my Safari windows. Screen image attached. Help!