https://www.bleepingcomputer.com/news/security/tech-support-scammers-lure-victims-with-fake-antivirus-billing-emails/

Tech support scammers are pretending to be from Microsoft, McAfee, and Norton to target users with fake antivirus billing renewals in a large-scale email campaign. 

While browsing the web, most people at one time or another have been redirected to a tech support scam web site that pretends your computer is infected and then prompts you to dial a displayed phone number.