Backdoor.Fearic

SUMMARY

Backdoor.Fearic is a backdoor Trojan horse that allows a hacker to use America Online Instant Messenger (AIM) or to open TCP/UDP ports to gain control of a computer.

Backdoor.Fearic is written in the Microsoft Visual Basic (VB) programming language. It will listen on ports 8811, 3456, and 2000.

NOTE: Symantec antivirus products detect the client portion of this Trojan as Backdoor.Fearic.Cli. The length of the client portion is 122,880 Bytes.

Protection

• Initial Rapid Release version August 8, 2002
• Latest Rapid Release version August 20, 2008 revision 017
• Initial Daily Certified version August 8, 2002
• Latest Daily Certified version August 20, 2008 revision 016
• Initial Weekly Certified release date August 14, 2002

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

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Backdoor.Fearic runs, it does the following:

It copies itself as C:\Windows\Config\Explorer.exe. The attribute of this file is set to hidden.

NOTE: Because the folder name C:\Windows\Config is hard coded in the Trojan program, the Trojan may not copy itself successfully into this location under Windows NT/2000/ XP systems if the folder does not already exist.

The Trojan inserts the following text into the [windows] section of the C:\Windows\Win.ini file:

[windows]
load=C:\windows\config\explorer.exe
open=C:\windows\config\explorer.exe

This causes the Trojan to run when you restart Windows.

Then the Trojan program will open TCP/UDP ports 8811, 3456, and 2000 and wait for the commands from the Hacker. It can also allow the hacker to use AIM to access the compromised computer.

This threat allows a hacker to perform a wide variety of actions on the compromised computer. The action can be any of (but not limited to) the following:

• Send information about the compromised computer to the hacker
• Control the AIM client on the compromised computer
• Download and upload files to or from the compromised computer
• Stealing or changing passwords or password files
• Keylogger
• Kill running processes
• Display messages
• Perform annoying actions: manipulate the mouse, show/hide Taskbar, open and close the CD tray, restart compromised computer, and so on

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.

REMOVAL

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, run a full system scan, and delete all files that are detected as Backdoor.Fearic or Backdoor.Fearic.Cli.
2. Remove the text that the Trojan added to the C:\Windows\Win.ini file.
   

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

To scan for and delete the infected files:

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate. LiveUpdate is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time 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 have undergone full quality assurance testing by Symantec Security Response. They 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.
     
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files.
   • Users of NAV Consumer products should read the document How to configure Norton AntiVirus to scan all files.
   • Users of NAV Enterprise products should read the document How to verify a Symantec Corporate antivirus product is set to scan all file.
     
3. Run a full system scan.
4. Delete all files that are detected as Backdoor.Fearic or Backdoor.Fearic.Cli.

To edit the Win.ini file:

NOTE: (For Windows Me users only) Due to the file protection process in Windows Me, there is a backup copy of the file you are about to edit in the C:\Windows\Recent folder. We recommend that you delete this file before you continue with the steps in this section. To do so using Windows Explorer, go to C:\Windows\Recent, and in the right pane select the Win.ini file and delete it. It will be regenerated as a copy of the file that you are about to edit when you save your changes to that file.

1. Click Start, and click Run.
2. Type the following, and then click OK.
   
   edit c:\windows\win.ini
   
   The MS-DOS Editor opens.
   
   NOTE: If Windows is installed in a different location, make the appropriate substitution.
   
3. In the [windows] section of the file, look for these two lines:
   
   Load = "C:\Windows\config\explorer.exe"
   Open = "C:\Windows\config\explorer.exe"
   
4. If they exist, select the entire line. Be sure that you do not select any other text, and then press Delete.
5. Click File, click Exit, and then click Yes to save the changes.