The design of such scam pages is similar to a system warning or a system update, but of course these web-pages have nothing to do with notifications from the operating system. The scam pages say that the visitor’s device is at risk and instructs victims to install programs that will help remove the virus, protect the device, and prevent identity theft. Your MAC might be at risk is a scam similar to the YOUR IPHONE HAS BEEN COMPROMISED scam aimed at iPhone owners.
The Your MAC might be at risk pop-ups are a scam