Troj/Agent-GCU is a Trojan for the Windows platform.
When run Troj/Agent-GCU creates the files:
<System>\toonjoke.dll - this file is detected as Troj/Agent-GCU
<System>\feelcat.ini - this file can be safely deleted.
Troj/Agent-GCU also installs itself into the Windows Socket Layer listening for network traffic.