Windows Functionality Checker is a fake Antivirus. This rogue displays fake alerts to scare users. It replaces Windows Protection Master, Home Safety Essentials, Anti-Malware Lab, System Smart Security, PC Security Guardian, Best Malware Protection, Internet Security Essentials, Smart Internet Protection 2011, Personal Internet Security 2011, Personal Security Sentinel, Internet Antivirus 2011, Internet Security Suite, Smart Security, My Security Shield, Security Master AV, My Security Engine, Security Guard, CleanUp Antivirus and Security Antivirus (family link)
Source: Windows Functionality Checker