The FTC is warning consumers about fake CAPTCHA screens popping up while people browse the web. The agency says the scam looks like a normal prove-you're-human check, but it tells users to open a Windows command box and paste in code. That can make the person install hidden malware on their computer. The FTC says scammers can then steal banking, email, and other login information. Real CAPTCHA checks do not ask people to run commands on a device.