Rule: -- Sid: 2100 -- Summary: Subseven 2.1 Gold is a Trojan Horse offering complete control of the infected host. -- 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. -- Detailed Information: This Trojan affects the following operating systems: Windows 95 Windows 98 Windows ME No other systems are affected. This is a windows executable that makes changes to the system registry, Win.ini and System.ini. When first executed the Trojan listens on either port 27374 or port 1243. Subseven is an improved version of the Netbus Trojan (see sids 114, 115), Subseven 2.1 Gold 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 server to programs normally started on boot. -- Attack Scenarios: This Trojan may be delivered to the target in a number of ways. This 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. -- False Positives: None Known -- False Negatives: None Known -- 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_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices Registry key added: Winloader Also affected: HKEY_CLASSES_ROOT\exefile\shell\open\command This registry key should be blank, i.e. "" The registry should also be searched for the entry HKEY_CLASSES_ROOT\.dl if this exists it should be deleted. This Trojan may also be started from the files win.ini and system.ini, remove the entry run=MSREXE.exe and change the line shell=Explorer.exe MSREXE.exe to the default value shell=explorer.exe. Removal of the Trojan is also required, look for the file "MSREXE.exe" in the <drive>:\Windows\ or <drive>:\Windows\System\ folders. Additionally, the files "RUN.EXE", "WINDOS.EXE" or "MUEEXE.EXE" may also be present on the system and should be removed along with any references to them in the start up locations in the same manner as for MSREXE.exe. Note, these file names are the default ones and can be changed by the attacker. A machine reboot is required to clear the existing process from running in memory. -- Contributors: Sourcefire Research Team Brian Caswell <bmc@sourcefire.com> Nigel Houghton <nigel.houghton@sourcefire.com> -- Additional References: Hackfix http://www.hackfix.org/subseven/ McAfee http://vil.mcafee.com/dispVirus.asp?virus_k=10566 Dark-e: http://www.dark-e.com/archive/trojans/subseven/gold/index.shtml --