Certified technicians then supposedly guide users through the malware removal process. Users are advised that they must not hesitate to call Apple technical support via the telephone number (' 1-84') provided. This error states that the system has been infected and that the malware must be removed and system repaired immediately. These programs also deliver various 'malvertising' ads (pop-ups, banners, coupons, etc.), record information (mostly, about web browsing habits), and misuse system resources. This error is displayed by a malicious website that users often visit inadvertently - they are redirected by various potentially unwanted programs (PUPs). 'WARNING! MAC OS Is Infected' is a fake error similar to Apple Security Alert, Apple Support Center - Attention!!, Apple Warning Alert, and many others. How to remove WARNING! MAC OS Is Infected from Mac?