[Snort-sigs] BACKDOOR NetMetro File List Signature False Positive

McCash, John John.McCash at ...2471...
Fri Aug 27 05:40:33 EDT 2004


Here's a suggested update for the 'BACKDOOR NetMetro File List' signature, which lists a possible false positive that I've just observed.
		John McCash


GEN:SID  	 1:159
Message 	BACKDOOR NetMetro File List
Rule 	alert tcp $EXTERNAL_NET any -> $HOME_NET 5032 (msg:"BACKDOOR NetMetro File List"; flow:to_server,established; content:"--"; reference:arachnids,79; classtype:misc-activity; sid:159; rev:6;)
Summary 	This event is generated when an attempt is made to list files on a host infected with the NetMetro Trojan Horse.
Impact 	Limited control of the target host.
Detailed Information 	Due to the nature of this Trojan it is unlikely that the attacker's client IP address has been spoofed.

The server portion opens TCP port 5031 by default to establish a connection between client and server.
Affected Systems 	Windows 95
    Windows 98
    Windows ME
    Windows NT
    Windows 2000
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.
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 NMS.exe.
False Positives 	This rule can generate a false positive if a web request goes out on port 5032, and is responded to by a web server with a string containing '--'
If you think this rule has a false positives, please help fill it out.
False Negatives 	None Known
If you think this rule has a false negatives, please help fill it out.
Corrective Action 	A reboot of the infected machine is recommended. The Trojan does not start automatically at boot time nor does it change any system registry settings.
Contributors 	Original Rule Writer Max Vision <vision at ...1729...>
Sourcefire Research Team
Nigel Houghton <nigel.houghton at ...435...>
Additional References 	Whitehats arachNIDS
http://www.whitehats.com/info/IDS79

Dark-e:
http://www.dark-e.com/archive/trojans/NetMetro/index.html
Rule References 	arachnids: 79
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