GEN:SID 1:147
Message BACKDOOR GateCrasher
Summary Gatecrasher is a Trojan Horse capable of stealing passwords and key
logging.
Impact Possible theft of data and passwords.
Detailed Information This Trojan affects the following operating systems:

    Windows 95
    Windows 98
    Windows ME

The Trojan changes system registry settings to add the Gatecrasher
server to programs normally started on boot. Due to the nature of this
Trojan it is unlikely that the attacker's client IP address has been
spoofed.
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.

The Trojan server is named system.exe
Corrective Action Edit the system registry to remove the extra keys or restore a
previously known good copy of the registry.

Affected registry keys are:

    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\

Registry keys added are:

    Command

Removal of this entry is required.

Delete the file system.exe

Ending the Trojan process is also necessary. A reboot of the infected
machine is recommended.
Additional References Whitehats arachNIDS
http://www.whitehats.com/info/IDS99
Rule References arachnids: 99