W32.Banleed.A

1. Copies itself as the following file:
   
   C:\Windows\system.exe
   
   
2. Checks for the presence of the following file and stops the execution if that file exists:
   
   C:\halt.txt
   
   
3. Adds the value:
   
   "[FILENAME]" = "[PATH TO WORM]"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   so that it runs every time Windows starts.
   
   
4. Creates and executes the following batch file to enumerate all the hosts in network shares of the infected machine:
   
   C:\Windows\system.bat
   
   
5. Creates the following files:
   
   
   • C:\Windows\view.txt - output of system.bat
   • C:\Windows\maq.txt - list of hosts in network shares
   • C:\Windows\okey.txt - clean text file
     
     
6. Attempts to spread across local network shares by copying itself on the startup folder of remote machines found. The worm tries to copy its executable in the following remote folder:
   
   \[NETWORK_HOST]\C$\Documents and Settings\All Users\Menu Iniciar\Programas\Inicializar
   
   NOTE: The worm uses a hardcoded path during its replication so that it will work only Brazilian/Spanish Windows machines.
   
   
7. Updates its code by downloading a configuration file from the following URL:
   
   [http://]www.rulandocash.net/upd/upd[REMOVED]
   
   The downloaded file contains the following configuration information:
   
   
   • version = [VERSION NUMBER]
   • download = [DOWNLOAD URL]
   • installdir = [INSTALL PATH]
     
     
8. Uses the configuration file to download the following remote file that at the time of writing was not available from the remote location:
   
   [http://]www.sinmadam.net/.%20/upd/lsas[REMOVED]
   
   
9. Saves the downloaded file as the following file and then executes it:
   
   c:\windows\system\NVSVC32.EXE
   
   
10. Monitors the browser windows of Internet Explorer and Firefox looking for any of the following bank URLs:
    
    
    • [https://]www2.bancobrasil.com.br/aapf/aai/logi[REMOVED]
    • [https://]internetcaixa.caixa.gov.br/nasapp/siibc/login_autent[REMOVED]
    • [https://]wwwss.bradesco.com.br/scripts/ib2k1.dll/lo[REMOVED]
    • [https://]net.sofisa.com.br/netbanking/tvirt[REMOVED]
    • [https://]bankline.itau.com.br/gripnet/gracg[REMOVED]
    • [https://]wwws.nossacaixa.com.br/bemvin[REMOVED]
    • [https://]www2.rural.com.br/ruralibank/princi[REMOVED]
    • [http://]www.unibanco.com.br/hom/inde[REMOVED]
    • [http://]www.equifax.com.br
    • [http://]www.tibia.com/ho[REMOVED]
    • [http://]login.passport.net/uilog[REMOVED]
    • [https://]www.orkut.com/glogi[REMOVED]
    • [http://]www.banespa.com.br/portal/bnp/script/templates/gcmreq[REMOVED]
      
      
      Depending on the URL entered into the browser, the worm hijacks the current browser window and displays its fraudulent Web page of the bank site as in the following examples:
      
      Bradesco bank URL example:
      
      
      
      Unibanco bank URL example:
      
      
      
      
11. Gathers this information and send it to a remote mail address, once the user enters his authentication information into the malicious Web page.
    
    
12. May contact the following remote site to retrieve the interenet IP address of the infected machine:
    
    [http://]checkip.dyndns.org

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.