BAT.Mumu.A.Worm

BAT.Mumu.A.Worm is a large collection of files that use each other to spread over administrative shares on Windows NT, 2000, and XP systems. The files associated with this worm are:

• 10.bat: A malicious batch file.
• hack.bat: A malicious batch file.
• hfind.exe: A Hacktool that will be detected as Hacktool.Hacline.
• ipc.bat: A malicious batch file.
• muma.bat: A malicious batch file.
• near.bat: A malicious batch file.
• ntservice.bat: A malicious batch file that stops the "Application" service, runs ntservice.exe with the -install argument, and then starts the "Application" service.
• ntservice.exe: A UPX-packed executable that will create a service described in NTService.ini.
• NTService.ini: Service information giving the name as "Application," it will run cmd.exe /c ss.bat.
• nwiz.exe: A legitimate application from nVidia.
• nwize.exe: Installer of the pcGhost utility.
• nwiz.in_: A configuration file.
• nwiz.ini: A configuration file.
• ipcpass.txt: A text file.
• tihuan.txt: A text file.
• rep.exe: A legitimate utility for replacing strings.
• psexec.exe: A legitimate utility from Sysinternals to remotely start the processes.
• random.bat: A malicious batch file.
• replace.bat: A malicious batch file.
• ss.bat: A batch file that will create an admin user, as well as run the psexec on the remote machine.
• start.bat: A malicious batch file.
• pcmsg.dll: A legitimate file from the pcGhost utility (not to be confused with the Symantec-cloning software, Ghost).
  

When this worm is executed, the execution occurs as follows:
Start.bat is executed first. This file will call several other files to perform the following actions on the system:

1. Finds all the files in drives C: to H: in the folder \MU (including subfolders), and then save them in the file, LAN.LOG. If any of the listed files contains the string "MU," nwiz.exe will be launched. When this process is completed, LAN.LOG will be deleted.
   
   
2. Deletes the file, ipcfind.txt, and calls the hacktool Hfind.exe, which Norton AntiVirus detects as Hacktool.Hacline. The command line parameter passed to this file will be a range of IP addresses. The range will start with the first two octets of the IP address (which have been randomized) with .0.1 added, and the end with the same first two octets of the IP address, but with .255.255 added.
   
   Hfind.exe will attempt to find the password for the administrative shares and save this information in a file named ipcfind.txt. The tool will use the following passwords:
   
   password
   passwd
   admin
   pass
   123
   1234
   12345
   123456
   <blank>
   
   
3. Replaces the Tihuan.txt file with ipcfind.txt.
   
   
4. For any account that Hfind.exe has discovered, the worm attempts to copy all the aforementioned files to the %System% folder using the administrative shares.
   
   NOTE: %System% is a variable. The worm locates the System folder and copies itself 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).
   
   
5. If the files were successfully copied, the worm will attempt to launch start.bat using the tool psexec.exe. This will effectively start the worm on the remote machine.
   
   
6. The worm will run the netstat command on the system. Then, it will attempt to call the batch file, Near.bat, supplying it with IP addresses.
   
   
7. Under Windows NT/2000/XP, the worm will create a service, the default name is "Application." This service will cause the ss.bat file to run every time windows starts.
   
   
8. Ss.bat creates or modifies the account named admin, assigns it the password of KKKKKKK, and then adds it to the Administrators group.
   
   

The Nwiz.ini and Nwiz.in_ files are identical. They are supposedly configuration files for nwiz.exe. However, they contain several strings that have been trivially encrypted. Decrypted, they contain information required to log in to an email server and send email. It is therefore possible that the author intended to use these strings to send himself/herself information from the infected systems. However, the author ostensibly had some errors in his/her logic, as this functionality does not work as intended.

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.

Summary