Rule:

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Sid:
147

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Summary:
Gatecrasher is a Trojan Horse capable of stealing passwords and key 
logging.

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Impact:
Possible theft of data and passwords.

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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.

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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:

Whitehats arachNIDS
http://www.whitehats.com/info/IDS99

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