Backdoor.Graybird.C

SUMMARY

Backdoor.Graybird.C is a Backdoor Trojan and a variant of Backdoor.Graybird. It gives a hacker unauthorized access to your computer. It opens port 52013 to listen for commands. The existence of the file, HGZSERVER.EXE, is an indication of a possible infection.

The Trojan uses this icon:



to attempt to disguise itself as an ordinary .txt file.

This threat is written in Delphi.

Protection

• Virus Definitions (LiveUpdate™ Weekly) April 16, 2003
• Virus Definitions (Intelligent Updater) April 16, 2003

Threat Assessment

Wild

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

Damage

• Damage Level: Medium
• Compromises Security Settings: Allows unauthorized remote access to an infected computer.

Distribution

• Distribution Level: Low
• Ports: 21, 52013

TECHNICAL DETAILS

When Backdoor.Graybird.C runs, it performs the following actions:

1. Copies itself as %System%HgzServer.exe.
   
   NOTE: %System% is a variable. The Trojan locates the System folder and copies itself to that location. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   
   
2. Creates the value:
   
   huigezi %System%HgzServer.exe
   
   in the registry keys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   RunServices
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun
   
   so that the Trojan runs when you start Windows.
   
   
3. If the operating system is Windows 95/98/Me, the Trojan adds the line:
   
   run=%System%HgzServer.exe
   
   to the [windows] section of the Win.ini file so that the Trojan runs when you start Windows.
   
   
4. Starts an FTP server on port 21, which allows the hacker to use the compromised computer as a temporary storage device.
   
   
5. Listens on port 52013 and waits for the commands from the hacker to perform unauthorized actions.

Recommendations

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

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

REMOVAL

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions.
2. Do one of the following:
   • Windows 95/98/Me: Restart the computer in Safe mode.
   • Windows NT/2000/XP: End the Trojan process.
3. Run a full system scan and delete all the files detected as Backdoor.Graybird.C.
4. Reverse the changes that the Trojan made to the registry.
5. Reverse the changes that the Trojan made to the Win.ini file (Windows 95/98/Me only).
   

For details on each of these steps, read the following instructions.

1. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

• Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
• Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).
  
  The 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. Restarting the computer in Safe mode or ending the Trojan process

Windows 95/98/Me
Restart the computer in Safe mode. All the Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document, "How to start the computer in Safe Mode."

Windows NT/2000/XP
To end the Trojan process:
1. Press Ctrl+Alt+Delete once.
2. Click Task Manager.
3. Click the Processes tab.
4. Double-click the Image Name column header to alphabetically sort the processes.
5. Scroll through the list and look for HgzServer.exe.
6. If you find the file, click it, and then click End Process.
7. Exit the Task Manager.
   

3. Scanning for and deleting the infected files

1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
   • For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
   • For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan All Files."
2. Run a full system scan.
3. If any files are detected as infected with Backdoor.Graybird.C, click Delete.

4. Reversing the changes made to the registry

CAUTION: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.

1. Click Start, and then click Run. (The Run dialog box appears.)
   
2. Type regedit
   
   Then click OK. (The Registry Editor opens.)
   
3. Navigate to each of these the keys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   RunServices
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun
   
   NOTE: All the keys do not exist on all the systems.
   
4. For each one, in the right pane, delete the value:
   
   huigezi %System%HgzServer.exe
   
5. Exit the registry editor.
   

4. Reversing the changes made to the Win.ini file
If you are running Windows 95/98/Me, follow these steps:

1. The function you perform depends on your operating system:
   • Windows 95/98: Go to step b.
   • Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the Win.ini file that you need to edit. If this backup copy exists, it will be in the C:WindowsRecent folder. Symantec recommends deleting this file before continuing with the steps in this section. To do this:
     1. Start Windows Explorer.
     2. Browse to and select the C:WindowsRecent folder.
     3. In the right pane, select the Win.ini file and delete it. The Win.ini file will be regenerated when you save your changes to it in step f.
        
        
2. Click Start, and then click Run.
   
3. Type the following:
   
   edit c:windowswin.ini
   
   and then click OK. (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
4. In the [windows] section of the file, look for a line similar to:
   
   run=C:WINDOWSSYSTEMHgzServer.exe
   
5. If this line exists, delete the entire line.
   
6. Click File, and then click Save.
   
7. Click File, and then click Exit.