W32.Netspree.Worm

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Discovered: January 22, 2003
Updated: February 13, 2007 11:45:53 AM
Type: Worm
Systems Affected: Windows


W32.Netspree.Worm is a worm that spreads over the network shares that are protected with trivial passwords.

W32.Netspree.Worm also uses IRC to notify the remote attackers when it infects a new system. This action may allow a hacker to download programs to the infected computer. The worm may also enable the hacker to use the infected computer as a drone for attacks against other internet-connected computers.

W32.Netspree.Worm does not spread from Windows 95/98/Me systems, although it functions normally in every other way on those platforms.

Antivirus Protection Dates

  • Initial Rapid Release version January 23, 2003
  • Latest Rapid Release version May 07, 2019 revision 006
  • Initial Daily Certified version January 23, 2003
  • Latest Daily Certified version May 07, 2019 revision 008
  • Initial Weekly Certified release date January 29, 2003

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


Technical Description


The W32.Netspree.Worm consists of these files:

  1. Lcp_Netbios.dll
  2. Psexec.bat
  3. Psexec.exe (A Sysinternals remote execution tool)
  4. Psexecsvc.exe (A portion of Psexec.exe)
  5. Win32load.exe

The Lcp_Netbios.dll, Psexec.bat, and Win32load.exe files are described in detail below.

Notes:
  1. Psexec.exe and Psexecsvc.exe are not malicious, and Symantec antivirus products will not detect them as such. These files will normally be copied to the %System% folder.
  2. %System% is a variable. The worm locates the System folder and copies the files to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
  • Lcp_Netbios.dll

    Lcp_netbios.dll is an NT service that contains the other four files. Lcp_netbios.dll inserts the files on your system, and then executes Psexec.bat.

  • Psexec.bat

    Psexec.bat is a simple batch file that takes in, as an argument, the system IP address to be probed.

    Psexec.bat consists of approximately 40 lines of this text:

    "net use \\%1\ipc$ <some password> /user:<some user name>"

    which probes the IPC$ using trivial user/password combinations (including username/nopassword). Then, it is terminated with a few lines that uses the Psexec.exe file to copy Win32load.exe to the remote system, and then executes it. This will only succeed if an open IPC$ share is found.

    The destination folder of the Win32load.exe file is %windir%\System32 and is hardcoded into the Psexec.exe utility.

  • WIN32LOAD.EXE

    When Win32load.exe is executed, it:
    1. Copies itself to the %system% folder, and then executes the copied file.
    2. Creates the registry value:

      Windows SubSys "<current execution path>\WIN32LOAD.EXE" rundll32.dll,loadsubsys,loadsys,win32

      under the registry keys:

      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
    3. Sets the registry value:

      restrictanonymous DWORD:0

      under the registry key:

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa

      Win32load.exe will wait for an active Internet connection. When one is found, it connects to the IRC server master.leet-gamer.net through port 6,667 and joins the channel #lc_breed using a hardcoded password. Then, Win32load.exe will announce its presence divulging information (to anyone who wants to listen) regarding vital information about the infected computer, including the IP address, system type, operating system, cpu type, and so on.

      Win32load.exe also contains rudimentary remote control functionality allowing for file downloading and execution. It also allows the computer to be used as a drone in a joint DoS attack against other Internet-connected computers.
    4. Downloads and executes Lcp_netbios.dll from a remote Internet site so that the cycle can continue.

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.


Removal


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. Do one of the following:
    • Windows 95/98/Me: Restart the computer in Safe mode.
    • Windows NT/2000/XP: End the Trojan process.
  3. Run a full system scan and delete all the files detected as W32.Netspree.Worm.
  4. Reverse the changes that the Trojan made to the registry.
For 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. Restarting the computer in Safe mode or ending the Trojan process
    • Windows 95/98/Me
      Restart the computer in Safe mode. All the Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document, "How to start the computer in Safe Mode."
    • Windows NT/2000/XP
      To end the Trojan process:
      1. Press Ctrl+Alt+Delete once.
      2. Click Task Manager.
      3. Click the Processes tab.
      4. Double-click the Image Name column header to alphabetically sort the processes.
      5. Scroll through the list and look for Win32load.
      6. If you find the file, click it, and then click End Process.
      7. Exit the Task Manager.
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 W32.Netspree.Worm, click Delete.

4. Reversing the changes made to 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_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  4. In the right pane, delete the value:

    Windows SubSys
  5. Navigate to the key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Runservices

    NOTE: This key will not exist on all systems.
  6. In the right pane, delete the value:

    Windows SubSys
  7. Navigate to the key:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
  8. In the right pane, double-click:

    restrictanonymous
  9. Change the value to:

    DWORD:1
  10. Exit the Registry Editor.


Writeup By: Atli Gudmundsson