Rule:

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Sid:
152, 157-158

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Summary:
Backdoor.Backconstruction is a Trojan Horse.

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Impact:
Possible theft of data via download, upload of files, execution of files
and reboot the targeted machine.

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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 Backconstruction
sever 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.

	SID	Message
	---	-------
	152	BackConstruction 2.1 Connection (outgoing TCP
connection)
	157	BackConstruction 2.1 Client FTP Open Request (incoming
TCP connection)
	158	BackConstruction 2.1 Server FTP Open Reply (outging TCP
connection)

This Trojan is commonly used to install other Trojan programs.

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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 located at <drive>:\WINDOWS\Cmctl32.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:

	Shell = "<drive>:\WINDOWS\Cmctl32.exe"

Removal of this entry is required.

Delete the file <drive>:\WINDOWS\Cmctl32.exe

Ending the Trojan process is also necessary. A reboot of the infected
machine is recommended.

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Contributors:
Original Rule Writer Max Vision <vision@whitehats.com>
Sourcefire Research Team
Brian Caswell <bmc@sourcefire.com>
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

Whitehats arachNIDS
http://www.whitehats.com/info/IDS505

Dark-e:
http://www.dark-e.com/archive/trojans/backc/21/index.shtml

Pest Patrol:
www.pestpatrol.com/PestInfo/b/back_construction.asp

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