Please note there are other methods for injecting the rogue applied. You PC may be compromised without your installing any applications.
Remove Win 8 Security System along with the rootkit installed in one kit with the fraudware. Rootkit is a sophisticated program lurking beyond operating system. It is not available for observation by system administrator, and tries to hide other malicious programs installed as regular Windows software.
Advanced free scan technology to get rid of Win 8 Security System scareware along with the rootkit, as well as other threats detected, is available here.