GEN:SID 1:185
Message BACKDOOR CDK
Summary CDK is a Trojan Horse offering the attacker control of the victim host.
This event is generated when an attacker connects to a victim server.
Impact Possible theft of data and control of the targeted machine leading to a
compromise of all resources the machine is connected to.
Detailed Information This Trojan affects the following operating systems:

    Windows 95
    Windows 98
    Windows ME
    Windows NT
    Windows 2000
    Windows XP
Affected Systems  
Attack Scenarios This Trojan may be delivered to the target in a number of ways. This
event is indicative of an existing infection being activated. Initial
compromise can be in the form of a Win32 installation program that may
use the extension ".jpg" or ".bmp" when delivered via e-mail for
example.
Ease of Attack This is Trojan activity, the target machine may already be compromised.
Updated virus definition files are essential in detecting this Trojan.
Corrective Action Restore a previously known good copy of the registry.

A reboot of the infected machine is recommended.
Additional References Whitehats arachNIDS
http://www.whitehats.com/info/IDS263
Rule References arachnids: 263