Backdoor.NetDevil.B

Printer Friendly Page

Discovered: December 27, 2002
Updated: February 13, 2007 11:39:59 AM
Type: Trojan Horse
Systems Affected: Windows



Backdoor.NetDevil.B is a variant of Backdoor.NetDevil . The Trojan allows a hacker to remotely control the infected computer. The Trojan opens port 905 for listening.

Antivirus Protection Dates

  • Initial Rapid Release version December 27, 2002
  • Latest Rapid Release version August 20, 2008 revision 017
  • Initial Daily Certified version December 27, 2002
  • Latest Daily Certified version August 20, 2008 revision 016
  • Initial Weekly Certified release date December 30, 2002

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Robert X Wang

Discovered: December 27, 2002
Updated: February 13, 2007 11:39:59 AM
Type: Trojan Horse
Systems Affected: Windows


When Backdoor.NetDevil.B runs, it does the following:

First, the Trojan copies itself as %system%\Kernel.dli

NOTES:

  • The file name is very similar to, and should not be confused with, Windows system file Kernel.dll
  • %system% is a variable. The Trojan locates the System folder and copies itself to that location. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

Next, the Trojan creates the following registry keys, each of which may contain multiple values:

HKEY_CLASS_ROOT\.dli    
HKEY_CLASS_ROOT\dlifile

NOTE: Do not confuse these with the legitimate registry keys HKEY_CLASS_ROOT\.dll and HKEY_CLASS_ROOT\dllfile

As a result, this allows a file that has the .dli extension to be executed as a .exe file.

Next, the Trojan adds the value

kernel32    <system>\Kernel.dli

to the registry key

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

so that the Trojan runs each time that you start Windows.

The Trojan listens on port 905 and sends your IP address, port number, and password to the hacker. This allows the hacker to remotely control the infected computer.

For additional information, please refer to the Backdoor.NetDevil writeup.

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: Robert X Wang

Discovered: December 27, 2002
Updated: February 13, 2007 11:39:59 AM
Type: Trojan Horse
Systems Affected: Windows


NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Update the virus definitions.
  2. Run a full system scan, and delete all files that are detected as Backdoor.NetDevil.B.
  3. Delete the value

    kernel32

    from the registry key

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  4. Delete the registry key

    HKEY_CLASS_ROOT\.dlI    (Note: The registry key name is .dlI but not .dll)
  5. Delete the registry key

    HKEY_CLASS_ROOT\dlIfile (Note: The registry key name is dlIfile but not dllfile)

For details on how to do this, read the following instructions.

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers once each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
  • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.

    Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

To scan for and delete the infected files:
  1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
  2. Run a full system scan.
  3. If any files are detected as infected with Backdoor.NetDevil.B, click Delete.

To delete the value from the registry:

CAUTION : Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Navigate to the key

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  4. In the right pane, delete the value

    kernel32
  5. Navigate to and delete the registry key

    HKEY_CLASS_ROOT\.dli

    CAUTION: Make sure that you do not delete the HKEY_CLASS_ROOT\.dll key.
  6. Navigate to and delete the registry key

    HKEY_CLASS_ROOT\dlIfile

    CAUTION: Make sure that you do not delete the HKEY_CLASS_ROOT\.dll key.
  7. Exit the Registry Editor.


Writeup By: Robert X Wang