Backdoor.Subseven.22.a

SUMMARY

Backdoor.Subseven.22.a is version 2.2 of the SubSeven backdoor Trojan. Backdoor.Subseven.22.a behaves similar to Netbus or BackOrifice.

Behavior

Symptoms

Transmission

Protection

• Virus Definitions (Intelligent Updater) March 14, 2001

Threat Assessment

Wild

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

Damage

• Damage Level: Low
• Releases Confidential Info: Passwords and other confidential files may be copied from your system.
• Compromises Security Settings: Allows other intruders to have unauthorized access on your system.

Distribution

• Distribution Level: Low
• Ports: variable (e.g. 1369)

TECHNICAL DETAILS

Backdoor.Subseven.22.a acts as the server application that allows a remote user to control and retrieve information from your system. Some of the capabilities include searching, retrieving, and sending files, stealing passwords, changing the colors and resolution, playing sounds, and changing the date and time.

When executed for the first time, this program will install itself to the WindowsSystem folder using a configurable name. The following registry key is also added with multiple entries:

HKEY_LOCAL_MACHINESoftwareMicrosoftENC

Once the server program is installed, the client program can access the server on a predefined, configurable port. The remote user can be notified that the server application has been installed on your system. The server can send a page using ICQ, send a notification by IRC, or send an email message.

The default server program is packed with UPX, so it may be variable in size, depending on the type and version of packer used.

The server is executed upon Windows startup. Either the Windows registry, Win.ini, or System.ini is modified to run the program automatically. In one case that was reported,the file Ruoy.exe was dropped in the WindowsSystem folder.

Here is a sample snapshot of the client-side interface:



Here is a sample snapshot of the Editserver tool, a component of Backdoor Subseven 2.2.:



Here is a sample snapshot of the Static IP Notifier, a component of Backdoor Subseven 2.2:

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

To remove this Trojan, delete any files detected as Backdoor.Subseven.22.a or Subseven.22.plugin, and delete the key that the Trojan added to the registry .

NOTE: Please make sure that the Trojan that was detected by NAV is Backdoor.Subseven.22.a. This should not be confused with the Backdoor.SubsevenTrojan. If you cannot open program files, the computer is probably infected with Backdoor.Subseven ,not Backdoor.Subseven.22.a.

To delete the files:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and then run a full system scan, making sure that NAV is set to scan all files.
3. Delete any files detected as Backdoor.Subseven.22.a and Subseven.22.plugin.

To edit the registry:

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

1. Click Start, and then 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_MACHINESoftwareMicrosoftENC
   
   CAUTION: Make sure that you navigate all the way to the Enc subkey.
   
4. Press Delete and then click Yes to confirm.
5. Close the Registry editor.