Backdoor.IRC.Zcrew

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Discovered: February 13, 2003
Updated: February 13, 2007 11:43:02 AM
Also Known As: IRC/Flood.bi [McAfee], Backdoor.IRC.Zcrew [Kaspersky
Type: Trojan Horse
Systems Affected: Windows


Backdoor.IRC.Zcrew is a backdoor Trojan Horse that is similar to other backdoor IRC Trojans, such as Backdoor.IRC.Aladinz and Backdoor.IRC.Flood.

Backdoor.IRC.Zcrew is written as an IRC script and uses the mIRC client to connect to the Internet, where it notifies the attacker of its presence. The hacker can send various commands to an infected computer and take full control over it.

An infected computer can also be used to launch a ping flood attack against another computer at a specified IP address.

Antivirus Protection Dates

  • Initial Rapid Release version February 14, 2003
  • Latest Rapid Release version November 01, 2017 revision 033
  • Initial Daily Certified version February 14, 2003
  • Latest Daily Certified version November 28, 2017 revision 022
  • Initial Weekly Certified release date February 19, 2003

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Jason Pan

Discovered: February 13, 2003
Updated: February 13, 2007 11:43:02 AM
Also Known As: IRC/Flood.bi [McAfee], Backdoor.IRC.Zcrew [Kaspersky
Type: Trojan Horse
Systems Affected: Windows


When Backdoor.IRC.Zcrew is executed, it performs the following actions:

  1. Loads the script of Backdoor.IRC.Zcrew through mIRC.

  2. Creates the following files:

    • %System%\Bootdrv.dll *
    • %System%\Explore.dat
    • %System%\Explore.exe
    • %System%\Explorer.exe *
    • %System%\Iiscache.dll
    • %System%\Libparse.exe*
    • %System%\Moo.dll *
    • %System%\Navdb.dbx
    • %System%\Psexec.exe *
    • %System%\Rcfg.ini
    • %System%\Rconnect.conf
    • %System%\Rconnect.exe
    • %System%\Secure.bat
    • %System%\Str.vxd
    • %System%\Svchost32.exe
    • %System%\V32driver.bat
    • %System%\Web.swf

      Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  3. Launches%System%\Svchost32.exe to hide the mIRC windows running Backdoor.IRC.Zcrew.

  4. Drops the following file:

    %Windir%\explorer Uninstaller.exe

    Note: %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows or C:\Winnt.

  5. Drops the following files:

    • %Windir%\Web\Printers\images\Bootdrv.dll *
    • %Windir%\Web\Printers\images\Explore.dat
    • %Windir%\Web\Printers\images\Explore.exe
    • %Windir%\Web\Printers\images\Explorer.exe *
    • %Windir%\Web\Printers\images\Iiscache.dll
    • %Windir%\Web\Printers\images\Libparse.exe*
    • %Windir%\Web\Printers\images\Moo.dll *
    • %Windir%\Web\Printers\images\Navdb.dbx
    • %Windir%\Web\Printers\images\Psexec.exe *
    • %Windir%\Web\Printers\images\Rcfg.ini
    • %Windir%\Web\Printers\images\Rconnect.conf
    • %Windir%\Web\Printers\images\Rconnect.exe
    • %Windir%\Web\Printers\images\Secure.bat
    • %Windir%\Web\Printers\images\Str.vxd
    • %Windir%\Web\Printers\images\Svchost32.exe
    • %Windir%\Web\Printers\images\V32driver.bat
    • %Windir%\Web\Printers\images\Web.swf
    • %Windir%\Web\Printers\images\boywonder.dat
    • %Windir%\Web\Printers\images\commands.txt
    • %Windir%\Web\Printers\images\hidden32.exe
    • %Windir%\Web\Printers\images\Mdx.dll *
    • %Windir%\Web\Printers\images\Moo.dll *
    • %Windir%\Web\Printers\images\Views.mdx *

  6. Creates the following folder:

    %System%\www

  7. Creates the following files:

    • %System%\www\Mdx.dll *
    • %System%\www\Moo.dll *
    • %System%\www\Views.mdx *

      Note: All the files marked with an asterisk (*) are parts of commercial programs that this Trojan exploits. They are not malicious in themselves, and as such, Symantec antivirus products do not detect them.

  8. Adds the value:

    "ccreg" = "%System%\explorer.exe"

    to the registry subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    so that the risk runs every time Windows starts.

  9. Adds the value:

    "EXPLORE" = "%System%\explore.exe"

    to the registry subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    so that the risk runs every time Windows starts.

  10. May add the values:

    "UninstallString:" = " "c:\winnt\web\printers\images\explorer.exe" -uninstall"
    "DisplayName:" = "mIRC"

    to the registry subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\OBCD

  11. May create the following registry subkeys:

    HKEY_ALL_USERS\SOFTWARE\OBCD\DateUsed
    HKEY_ALL_USERS\SOFTWARE\WinRAR SFX

  12. Opens a back door and listens for commands from the remote attacker to execute the following commands:

    • Create the file, Blah.vbs, to launch a ping flood attack against an IP address
    • Flood UDP packages to an IP address
    • Scan the ports of an infected computer


Recommendations

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

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • 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.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a 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.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. 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.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Jason Pan

Discovered: February 13, 2003
Updated: February 13, 2007 11:43:02 AM
Also Known As: IRC/Flood.bi [McAfee], Backdoor.IRC.Zcrew [Kaspersky
Type: Trojan Horse
Systems Affected: Windows



These 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. Restart the computer in Safe mode.
  3. Run a full system scan and delete all the files detected.
  4. Delete the value added to the registry.

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 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: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

2. Restarting the computer in Safe mode
All the Windows 32-bit operating systems, except Windows NT, can be restarted in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode ."

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.
  2. Run a full system scan.
  3. If any files are detected as infected with Backdoor.IRC.Zcrew, click Delete.
  4. Using Windows Explorer, locate and delete the folder, %System%\www. (All the variants do not add this folder.)
4. To delete the value from the registry
Important: 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 subkeys only. For instructions refer to the document: How to make a backup of the Windows registry.
  1. Click Start > Run.
  2. Type regedit
  3. Click OK.

    Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.

  4. Navigate to the subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  5. In the right pane, delete the value:

    "ccreg" = "%System%\explorer.exe"

  6. Navigate to the subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  7. In the right pane, delete the value:

    "EXPLORE" = "%System%\explore.exe"

  8. Navigate to and delete the subkeys:

    HKEY_ALL_USERS\SOFTWARE\OBCD\DateUsed
    HKEY_ALL_USERS\SOFTWARE\WinRAR SFX

  9. Exit the Registry Editor.

Writeup By: Jason Pan