Rule:

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Sid:
103

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Summary:
Subseven22 is a Trojan Horse.

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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. Other versions are capable of launching DDoS attacks.

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Detailed Information:
This Trojan affects the following operating systems:

	Windows 95
	Windows 98
	Windows ME
	Windows NT
	Windows 2000
	Windows XP

No other systems are affected. This is a windows exceutable that makes 
changes to the system registry, Win.ini and System.ini. When first 
executed the Trojan replicates itself and in most cases, gives the copy 
a random name. This Trojan may use the file extensions ".exe" or ".dll".

Subseven is an improved version of the Netbus Trojan (see sids 114, 
115), Subseven DEFCON8 2.1 is an improved version of Subseven that 
affects Windows 95 and 98 implementations.

The Trojan changes system startup files and registry settings to add the
Subseven sever to programs normally started on boot.

	SID	Message
	---	-------
	103	subseven 22 (incoming TCP connection)
	107	subseven DEFCON8 2.1 access (outgoing TCP connection)

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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:

This is a particularly difficult Trojan to remove and should only be 
attempted by an experienced Windows Administrator.

Edit the system registry to remove the extra keys or restore a 
previously known good copy of the registry.

Affected registry keys are:

	HKEY_CLASSES_ROOT\exefile\shell\open\command
	HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Current Version\Run
	HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Current Version\RunServices
	HKEY_LOCAL_MACHINE\Hardware\Data
	HKEY_LOCAL_MACHINE\Hardware\Enum
	HKEY_LOCAL_MACHINE\Software\Microsoft\DirectXMedia

Registry keys added are:

	HKEY_CLASSES_ROOT\.dl

Removal of the replicant is also required, look for files ending in 
".exe" or ".dll" in the <drive>:\Windows\ or <drive>:\Windows\System\ 
folders that use alphanumeric file names. The name of the replicant may 
be in one of the registry keys above.

A machine reboot is required to clear the existing process from running 
in memory.

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

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Additional References:

Hackfix
http://www.hackfix.org/subseven/

McAfee
http://vil.mcafee.com/dispVirus.asp?virus_k=10566
http://vil.nai.com/vil/content/v_10566.htm

Symantec Security Response
http://securityresponse.symantec.com/avcenter/venc/data/backdoor.subseven22.html

F-Secure:
http://www.f-secure.com/v-descs/subseven.shtml

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