Rule:

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Sid:
3155

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Summary:
BackOrifice is a Trojan Horse.

Server Port: 31337 although in later versions this port can be changed
to a value between 1 and 65535 Protocol: UDP although in later versions
TCP can also be used

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Impact:
Possible theft of data and control of the targeted machine leading to a
compromise of all resources the machine is connected to. This Trojan
also has the ability to delete data, steal passwords and disable the
machine.

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Detailed Information:
The Trojan changes system registry settings to add the BackOrifice 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.

The default name of the server application is UMGR32, which can be
changed on first use. The new application may be installed in the system
or system32 direcory and the original may also be deleted.

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Affected Systems:
	Windows 95
	Windows 98
	Windows ME
	Windows NT

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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.

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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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

Registry keys added may vary, look for spurious entries in the above
locations.

BackOrifice may hide the process from viewing inthe Windows task
manager. A reboot of the infected machine is recommended.

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Contributors:
Sourcefire Research Team
Brian Caswell <bmc@sourcefire.com>
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

Symantec Security Response
http://www.symantec.com/avcenter/venc/data/back.orifice2000.trojan.html

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