macOS security center

Not a virus, it's a scam. You probably picked up adware from some shady download hosting site.

How to block pop-ups in Safari - Apple Support

You can effectively remove adware with MalwareBytes, written by one of our long-serving and respected contributors here. The free version is run manually but should take case of the occasional intrusion. The full version runs in the background blocking adware as you go,.

I've never had any problems with Malwarebytes. Perhaps you are running an anti-virus program or other junk that is causing the problem.

Try setting up another admin user account in System Preferences/Users & Groups to see if the same problem continues. Please post back on whether or not this worked. Also try the Safe Mode. Please post back on whether or not this worked.

Isolating an issue by using another user account 

Safe Mode - About

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor.  Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown. If the log won’t post, try posting it in Pastebin and provide a link in a reply. After pasting the report in a PasteBin page, go to the top of the page, and copy the address in the URL bar. Paste that in a new reply.        Pastebin

Etrecheck – System Information

Download link if you need it.

Malwarebytes Anti-Malware for Mac      10.10 and later

Malwarebytes uninstall

Thanks Eric.

You are welcome.

Doesn't run properly after install. Brings an error to restart the computer and contact the authors. Like most of these anti virus and malware stuff just as big a scam.