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Backdoor.SubSeven

Risk Level 1: Very Low

Discovered:
June 6, 1999
Updated:
February 13, 2007 11:50:13 AM
Type:
Trojan Horse
Systems Affected:
Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows XP

Backdoor.SubSeven is a Trojan Horse, similar to Netbus or Back Orifice. This Trojan enables unauthorized people to access your computer over the Internet without your knowledge.

When the server portion of the program runs on a computer, the individual who is remotely accessing the computer may be able to perform the following:
  • Set it up as an FTP server
  • Browse files on that system
  • Take screen shots
  • Capture real-time screen information
  • Open and close programs
  • Edit information in currently running programs
  • Show pop-up messages and dialog boxes
  • Hang up a dial-up connection
  • Remotely restart a computer
  • Open the CD-ROM
  • Edit the registry information

When BackDoor.Subseven is run, it makes the following changes to the system:
  • Drops (adds) a copy of itself and a randomly named executable file, such as Eutccec.exe, to the \Windows or \Windows\System folder.
  • Adds the dropped file to the load= and run= lines of the Win.ini file.
  • Adds the dropped filename to the shell=explorer.exe line of the System.ini file.
  • Creates the WinLoader value and sets it equal to the dropped filename in the registry keys below.
  • Modifies the (Default) value from "%1" %* to, for example, eutccec.exe "%1" %*, in the following registry keys:

    HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: George Koris
Summary| Technical Details| Removal

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