Dangerous Trojan is very similar to Unknown Trojan. It shows this fake message:
System Error! Your system was infected by dangerous Trojan. Note: Your critical files can be lost! Click OK to download antimalware application to clean your system! (Recommended)
and tries to scare you. It promotes Files Secure - fake-antispyware software.
It may change Yahoo and Google search engine result pages.

If u see this message:
“Your computer was infected by an Unknown Trojan. It’s dangerous for your system (critical files can be lost)! Click OK to download the antispyware program to clean your computer! (Recommended)”
dont be afraid. You don’t have trojan in your computer, it’s just a fake message of rogue anti-spyware software. This software must be remove immediately, cause it does not detect spyware it just show you fake messages trying you to scare into buying fake application.