Troj/Multidr-KN is a Trojan for the Windows platform.
The Trojan drops the following files and then runs them:
rar.exe (detected by Sophos's anti-virus products as Troj/Istbar-IS)
rar2.exe (Adware)
vonner.exe (detected by Sophos's anti-virus products as Troj/Multidr-KO)