Rule:

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Sid:
147

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Summary:
This event is generated when network traffic indicating the use of the Gatecrasher trojan horse is detected.

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Impact:
Possible theft of data and passwords.

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Detailed Information:
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.

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Affected Systems:
Windows 95
Windows 98
Windows ME

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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.

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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

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False Positives:
None Known

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False Negatives:
None Known

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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.

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Contributors:
Original rule written by Max Vision <vision@whitehats.com>
Sourcefire Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

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