The advertisement, first spotted by CBS News, appeared if a user typed "Amazon" into Google Search. It looked like a normal ad but, when clicked, it routed users to a Facebook page and tried to trick users into thinking their computer might be infected with malware.
A message that appeared to be an official notification from Microsoft then suggested that a user's financial data may have been compromised and to call a support number.
CBS said scammers answered the faux support number and claimed to work for Microsoft before asking for $150 to rid the computer of a virus that didn't exist. People who may have fallen for this scheme could have put their personal information, including credit card numbers, at risk.
Microsoft doesn't ask for this sort of information over the phone.
"We do not send unsolicited email messages or make unsolicited phone calls to request personal or financial information or fix your computer," Microsoft's privacy page says. "If you receive an unsolicited email message or phone call that purports to be from Microsoft and requests that you send personal information or click links, delete the message or hang up the phone."
A Google spokesperson told CNBC that the ad was an "abuse of our platform."
"We strictly prohibit advertising of illegal activity and have removed these ads and suspended the account," the spokesperson said. "When we find ads that violate our policies, we take immediate action to disable the offending sources."