Backdoor.Sixca

SUMMARY

The Backdoor.Sixca backdoor Trojan allows unauthorized access to the infected computer. By default, the Trojan attempts to listen on port 666. This Trojan is written in Microsoft Visual Basic and it requires that the Visual Basic (VB) run-time libraries be installed for it to execute.

Protection

• Virus Definitions (LiveUpdate™ Weekly) January 9, 2003
• Virus Definitions (Intelligent Updater) January 9, 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 access to the infected computer.

Distribution

• Distribution Level: Low
• Ports: 666

TECHNICAL DETAILS

When Backdoor.Sixca is executed, it does the following:

1. Adds the value:
   
   <filename> %System%<filename>.exe
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   NOTE:
   • <filename> is the file name of this Trojan, and it will vary.
   • %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. Checks for the existence of the file, %System%<filename>.exe.
   • If the file is not found on the computer, the Trojan moves itself as %system%<filename>.exe and quits.
   • If the file is found on the computer, the Trojan attempts to listen on port 666.
3. Waits for commands from the hacker to perform the following actions:
   • Open or close the CD-ROM drive
   • Logoff, restart, or shut down Windows
   • Obtain the system information
   • Obtain the cached passwords
   • List, create, or remove folders
   • Delete, create, copy, move, rename, execute, or read files
   • Format disks
   • Display message box and wait for the answer of the victim
   • Display blue or black screen
   • Shut down the Trojan

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

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.
2. Run a full system scan and write down the file names detected as Backdoor.Sixca, and then delete the files.
3. Delete any values that refer to the infected files from the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
4. Restart the computer and run another scan.

For specific details on each of these procedures, 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 the 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), in the "Protection" section, at the top of this writeup.
• 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), in the "Protection" section, at the top of this writeup.
  
  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. 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.Sixca, write down the file names, and then click Delete.
   
   NOTE: If your Symantec antivirus product is not able to delete a file, Windows is using this file. In this case, continue with the scan. Delete any such files in the last steps of the removal process.

3. Deleting the value from the registry

CAUTION: Symantec strongly recommends that you back up the registry before you make 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, and then click OK. (The Registry Editor opens.)
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete any values that refer to the infected file names you previously wrote down.
5. Exit the Registry Editor.

4. Restarting and scanning
Restart the computer and run another scan. Delete any files detected as infected with Backdoor.Sixca.