Zook is a Korea based software solution for remote access to your PC. It uses the RFB (Remote Frame Buffer) to create a VNC (Virtual Network Connection) to the PC. This is similar to Windows Remote Desktop Protocol.

This SonicWALL signature identifies Zook network traffic. SID 184, "Remote Frame Buffer (VNC) -- Connection Attempt" identifies the main remote access traffic to the PC, so this signature is also required.