BackOrifice2K.Trojan

SUMMARY

Back Orifice 2000 is a new version of BackOrifice.Trojan. When installed on a Microsoft Windows system, this backdoor trojan horse program allows others to gain full access to the system through a network connection. Similar to the original BackOrifice, it consists of two pieces: a server and a client application. However, now both applications are capable of running under Windows NT. The client application, running on one machine, may be used to monitor and control a second machine 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 UDP protocol is implemented. There have not been any reports of this program being able to break through a firewall.

Protection

• Virus Definitions (Intelligent Updater) July 11, 1999

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
• Target of Infection: Microsoft Windows 9x and NT

TECHNICAL DETAILS

Technical Notes

The server application may be configured with several different options. The networking protocol may be TCP or UDP. Any port number between 1 and 65535 may be selected for communication.

In the US version, the information transmitted may be encrypted by XOR or using 3DES. The 3DES encryption is not available in the international version.

The encryption key is programmable for both types of encryption. When the server program is executed for the first time on a system, it may copy itself to the WINDOWSSYSTEM directory on a Windows 9x system, and the WINNTSYSTEM32 directory on a Windows NT system. After being copied to the Windows system directory, the program may delete the original copy of itself. The name of the copied file is programmable. The default name of the copied executable begins with UMGR32. The server program may be configured to start itself upon Windows startup by adding an entry to the registry.

The program may also be set to hide itself from a process viewer such as Task Manager in Windows NT. If it is not hidden, the process name may be any name because it is also configurable. Plug-ins to this program may be integrated to add new functionality.

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

• Ping and query the server
• Reboot or lock up the system
• List cached and screen saver passwords
• Display system information
• Log keystrokes, view the keystroke log and delete the keystroke log
• Display a message box
• Map a port to another IP address, application, HTTP file server, or filename
• List ports mapped by BackOrifice 2000
• Send a file through another port
• Share a drive, unshare a drive, list shared drives, list shared devices on a LAN, mapped a shared device, unmap a shared device and list all connections
• List current processes, kill a process and start a process
• View and edit the registry - create a key, set a value, get a value, delete a key, delete a value, rename a key, rename a value, enumerate keys and enumerate values
• Video and audio capture and playback
• Capture a screen shot
• File and directory commands - list directory, find file, delete file, view file, move file, rename file, copy file, make directory, remove directory and set file attributes
• Receive and send files
• Compress and uncompress files
• Resolve host name and address
• Server control - shutdown server, restart server, load plug-in, remove plug-in and list plug-ins

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

Windows 9x Systems with NAV Installed

Note the name of the file NAV detects as the BackOrifice2k.Trojan. Reboot the machine to a clean DOS boot or Windows Startup floppy disk. Go to the WINDOWSSYSTEM directory on the drive where Windows is installed. Delete the file NAV detected as the BackOrifice2k.Trojan. Remove the floppy disk and restart the system. Edit the Windows registry using REGEDIT.EXE. Go to the following registry key:

HKEY_LOCAL_MACHINESoftwareMicrosoftWindows

CurrentVersionRunServices

Delete the value that contains the name of the file NAV detected as the BackOrifice2k.Trojan.

Windows NT Systems with NAV Installed

Note the name of the file NAV detects as the BackOrifice2k.Trojan. Edit the Windows registry using REGEDIT.EXE. If you have Administrator access, go to the following registry key:

HKEY_LOCAL_MACHINESYSTEMCurrentControlSet

Services

Press CTRL+F and enter the name of the file NAV detected as the BackOrifice2k.Trojan. Delete the entire registry key that contains this value. This will delete the key from all ControlSet registry keys (i.e., ControlSet01, ControlSet02, etc.). Then, restart the system. Once Windows has started, go into the Command Prompt in the Start/Programs... menu, and delete the file NAV detected as the BackOrifice2k.Trojan. Check the registry again to make sure the trojan did not reinstall itself. Follow the instructions below to check if the trojan was installed without Administrator access. For users without Administrator access, go to the following registry key:

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows

CurrentVersionRun

Check if the name of the file NAV detected as the BackOrifice2k.Trojan appears in this key. If so, delete that value from the registry. Then, restart the system. Once Windows has started, go into the Command Prompt in the Start/Programs... menu, and delete the file NAV detected as the BackOrifice2k.Trojan. Check the registry again to make sure that the trojan did not reinstall itself.

Windows 9x Systems without NAV Installed

If you do not have an antivirus product that detects this trojan, search through the following Windows 9x registry keys for any unusual entries:

HKEY_LOCAL_MACHINESoftwareMicrosoftWindows

CurrentVersionRunServices

The default server file name will start with UMGR32, but it can be any name. The data value will have WINDOWSSYSTEM followed by the file name in the string. Note the name of the file. Delete this value from the registry. Then, reboot the system to a clean DOS boot or Windows Startup floppy disk. Go to the WINDOWSSYSTEM directory on the drive where Windows is installed. Delete the file with the same name as the deleted registry value. Remove the floppy disk and restart the system. Check the registry again to make sure the trojan did not reinstall itself.

Windows NT Systems without NAV Installed

If you do not have an antivirus product that detects this trojan, you must search through the registry manually. For users with Administrator access, run REGEDIT.EXE, and look for unusual entries in the following registry key:

HKEY_LOCAL_MACHINESYSTEMCurrentControlSet

Services

The default key is Remote Administration Service nested in the key listed above, but it can have any key name. Note the name of the file listed for ImagePath. Delete the entire key. This will delete the key from all ControlSet registry keys (i.e., ControlSet01, ControlSet02, etc.). Then, restart the system. Once Windows has started, go into the Command Prompt in the Start/Programs... menu, and delete the file listed for ImagePath in the deleted registry key. Restart the system, and check the registry again to make sure the trojan did not reinstall itself. Follow the instructions below to check if the program was installed without Administrator access. For users without Administrator access, run REGEDIT.EXE, and look in the following registry key:

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows

CurrentVersionRun

Search for any unusual entries that have WINNTSYSTEM32 in the data field. Note the name of the file that follows WINNTSYSTEM32. Delete this registry value. Then, restart the system. Once Windows has started, go into the Command Prompt in the Start/Programs... menu, and delete the file listed in the deleted registry value. Restart the system, and check the registry again to make sure the trojan did not reinstall itself. Contact your administrator to check if the trojan horse program was installed with Administrator access.