DonaldD.Trojan

SUMMARY

The DonaldD.Trojan is similar to the BackOrifice.Trojan. When installed in Microsoft Windows, this backdoor Trojan horse program enables others to gain full access to the system through a network connection. It consists of two parts: a server application and a client application. Both applications can run under Windows 95, 98, and NT 4.0. The client application, running on one computer, may be used to monitor and control a second computer running the server application.

The port number through which the client controls the server is configurable. However, as long as the port is blocked by a firewall, this Trojan horse will not be able to infiltrate the server. It does not matter whether the TCP or SPX protocol is implemented. There have not been any reports of this program being able to break through a firewall.

Protection

• Virus Definitions (Intelligent Updater) September 28, 1999

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 3 - 9
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: High
• Releases Confidential Info: Allows unauthorized access to infected computers
• Compromises Security Settings: See Technical description

Distribution

• Distribution Level: Low
• Ports: TCP: 23476, 23477 SPX: 0x9014, 0x9015

TECHNICAL DETAILS

The server application may be configured with several different options.

The networking protocol may be TCP or SPX. Any port number between 1 and 65535 may be selected for communication. The default port number for TCP is 23476, and an additional default port is 23477. For SPX, it is 0x9014 and an additional default port is 0x9015.

A password may be specified to limit the access on a server. However, there is a bug in version 1.52 of the Trojan. In the client GUI, the password typed in is initially hashed using MD5 and is converted to a 32-byte string, which is the hex representation. Then the result is sent to the server. For the command-line version of the client, the password is sent without using any type of encryption. Thus, if a user sets the password of the server using the command-line client, then they cannot access it again by using the GUI client with the same password.

Additional bugs found in version 1.52 of this Trojan:

• When the client attempts to play a .wav file to the server, and the client does not specify a file name in this field, the client program crashes.
• The same situation occurs when the client user forgets to specify the path for the server upgrade command.

The following is a list of commands the client program may send to the server program:

• Create and delete directories
• Copy, delete, rename, upload, and download files
• View, terminate, and set priorities for processes
• Suspend and resume threads
• Execute programs
• Create and delete registry keys
• Set registry values
• Modify system date and time
• Perform a shutdown, logoff, restart, and power-off
• Obtain a list of windows opened
• Get a snapshot of the entire screen or just for a specific window
• Send messages to a specific window
• Modify CMOS (this currently works only in Windows 95/98)
• Look at the contents of the buffer where the keyboard input is stored
• Remap and disable keys of the keyboard
• Simulate certain keystrokes (only works in Windows 95/98)
• Open and close the CD-ROM tray
• Turn the monitor on and off
• Send message boxes with a few sets of buttons to choose from
• Play .wav files
• Chat with other people
• Obtain CMOS and screen saver passwords
• Query a list of shared resources

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

How you remove this Trojan depends on your version of Windows.

Windows 95/98
If you are running Windows 95/98, then follow these instructions. You will need an uninfected DOS boot disk or a Windows Startup disk.

Run a full system scan
Make sure that you have the most recent virus definitions, and run a full system scan, making sure that Norton AntiVirus (NAV) is set to scan all files. Write down the names of any files infected with the DonaldD.Trojan. Have NAV delete them if possible; in most cases it will not be able to do so. When finished, go on to the next section.

Delete files in DOS
Follow these steps to remove any infected files that could not be deleted by NAV:

1. Shut down Windows, turn off the power, and then wait thirty seconds. Do not simply press the reset button.
2. Insert a clean DOS boot disk or Windows Startup disk into the floppy disk drive.
3. Restart the computer. It will boot to a DOS prompt.
4. Type the following, and then press Enter:
   
   cd windowssystem
   
   NOTE: If Windows is installed in a folder other than C:Windows, change the prededing command accordingly.
   
5. Type the following, and then press Enter:
   
   del <filename>
   
   where <filename> is the name of the file that you wrote down when you ran the scan. For example, if NAV found an infected file named Badthing.exe, then type del badthing.exe
   
6. Remove the floppy disk, and then restart the computer.

Edit the Windows registry
Follow these steps to remove a registry entry that was added by the Trojan:

CAUTION: We strongly recommend that you back up the system registry before making any changes to it. Incorrect changes to the registry may result in permanent data loss or corrupted files. Be sure to modify the specified keys only. See the document How to back up the Windows registry before proceeding.

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 and select the following subkey:
   
   HKEY_LOCAL_MACHINESystemCurrentControlSetServicesVxDVMLDR
   
4. Press Delete, and then click Yes to confirm.
5. Click the Registry menu, and click Exit to save the changes and close the Registry Editor.

Windows NT

If you are running Windows NT, then follow these instructions. You will need an uninfected DOS boot disk or a Windows Startup disk.

Run a full system scan
Make sure that you have the most recent virus definitions, and run a full system scan, making sure that Norton AntiVirus (NAV) is set to scan all files. Write down the names of any files infected with the DonaldD.Trojan. Have NAV delete them if possible; in most cases it will not be able to do so. When finished, go on to the next section.

Edit the Windows registry
Follow these steps to remove a registry entry that was added by the Trojan:

CAUTION: We strongly recommend that you back up the system registry before making any changes to it. Incorrect changes to the registry may result in permanent data loss or corrupted files. Be sure to modify the specified keys only. See the document How to back up the Windows registry before proceeding.

NOTE: You must be logged on as Administrator.

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 and select the following subkey:
   
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession Manager
   
4. In the right pane, double-click BootExecute.
5. In the Edit Binary Value box, look for and select the following hexadecimal numbers:
   
   00 62 6F 6F 74 65 78 65 63
   
   
6. Select these numbers only, and then delete them.
7. Click OK.
8. In the right pane, select and delete the following values:
   
   Pdata0
   Pdata1
   
9. Exit the Registry Editor, and then restart the computer.

Delete files
Use Find Files to locate and delete any files that NAV could not delete.