Is this a legitimate Microsoft phone number? If not, how might have detect and remove the spyware?"
866-538-2493 is a scam that should be removed
Mind you, 866-538-2493 is not a legitimate Microsoft phone number. As a matter of fact, it is merely a scam used by scammers to promote fake tech support services and useless antivirus programs. Never take in! Basically, the 866-538-2493 pop-up is mainly caused by an adware or a potentially unwanted program that can make unauthorized modifications on your browser settings, which can cause pop-up ads, redirects, homepage hijacking, and other unsolicited actions