BAT.Boohoo.Worm

SUMMARY

BAT.Boohoo.Worm is a collection of batch files and utilities that copies itself across network shares that have weak administrator passwords. The worm establishes backdoor access to a compromised system using IRC on the IRC server port 6666 or 7000.

Protection

• Virus Definitions (LiveUpdate™ Weekly) July 30, 2003
• Virus Definitions (Intelligent Updater) July 28, 2003

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Low
• Compromises Security Settings: Starts a Backdoor Trojan and FTP server.

Distribution

• Distribution Level: Medium
• Ports: 6666, 7000
• Shared Drives: Copies itself to administrative shares with weak passwords.

TECHNICAL DETAILS

BAT.Boohoo.Worm consists of the following files:

• Malicious components that Symantec antivirus products detect:
  • hacker.bat BAT.Boohoo.Worm
  • ip.bat BAT.Boohoo.Worm
  • scan.bat BAT.Boohoo.Worm
  • starter.bat BAT.Boohoo.Worm
  • Xecuter.bat BAT.Boohoo.Worm
  • psexec.bat BAT.Boohoo.Worm
  • regkeyadd.REG BAT.Boohoo.Worm
  • ntscan.exe Hacktool
  
  
• Legitimate programs and harmless data files that Symantec antivirus products do not detect:
  • drvrquery32.exe Serv-U FTP server
  • CYGWIN1.dll legitimate dll
  • CommonDlg32.dll legitimate dll
  • Firedaemon.exe used to set up services
  • HideRun.exe used to hide processes
  • clearlogs.exe used to clear system logs
  • psexec.exe used to remotely start processes
  • random.exe random number generator
  • NT-pass.dic data file used by ntscan.exe
  • NT-user.dic data file used by ntscan.exe
  • rep.EXE used to edit the output of ntscan.exe
  • rep.bat used to edit the output of ntscan.exe
  • replace.txt used to edit the output of ntscan.exe
  • proreset.txt configuration file for the backdoor
  • protmp.txt configuration file for the backdoor
  • pro.gif configuration file for the backdoor
  • sys.txt text file
  • wm.txt text file
  • service.exe used to manage services
  • svhost.exe iroffer IRC fileserver

When BAT.Boohoo.Worm is executed, it does the following:

1. Copies the aforementioned files to the %Windir%System32 folder, and then adds the Hidden attribute to the System32 folder.
   
   
2. Creates a new user "admin1," and then adds it to the administrators group.
   
   
3. Creates services for the following programs, using Firedaemon:
   
   Service: Program:
   Startupdll Psexec.bat (startup script)
   Msinet Svhost.exe (irc backdoor)
   Drvmanager Drvrquery32.exe (ftp server)
   
   Svhost.exe is a backdoor based on iroffer, which is an irc-based file server. It connects to one of several irc servers on port 6666 or 7000.
   
   Drvrquery32.exe is a Serv-U FTP server.
   
   
4. Adds the following values:
   
   "drvrmanager"="c:winntsystem32drvrquery32.exe /S"
   "HideRun.exe"="c:winntsystem32Hiderun.exe c:winntsystem32svhost.exe c:winntsystem32pro.gif"
   "Xecuter.bat"="c:winntsystem32psexec.bat"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   so that the worm runs when you start Windows.
   
   
5. Adds the values:
   
   "AutoShareWKS"="0"
   "AutoShareServer"="0"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESystemCurrentControlSetServiceslanmanserverparameters
   
   
6. Removes network shares C$ through Z$.
   
   
7. Pings random IP addresses until it gets a response. Then, it checks a range of nearby addresses for weak passwords using ntscan.exe.
   
   It tries the following usernames:
   administrator
   admin
   
   and the following passwords:
   %null%
   %username%
   %username%12
   %username%123
   %username%1234
   123
   1234
   12345
   123456
   1234567
   12345678
   654321
   54321
   1
   pass
   password
   admin
   administrator
   root
   test
   super
   
   
8. For each account that the worm finds with a weak password, it tries to establish a connection and copy itself to one of the following:
   • admin$system32
   • c$winntsystem32
   • d$winntsystem32

If successful, the worm then uses Psexec to start itself on the remote computer.

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

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Disable System Restore (Windows Me/XP).
2. Find and stop processes.
3. Find and stop services.
4. Delete the modifications made to the registry.
5. Update the virus definitions.
6. Run a full system scan and delete all the files detected as BAT.Boohoo.Worm, Backdoor.Trojan, or Hacktool. Delete any additional undetected and unwanted files mentioned above.

For specific details on each of these steps, read the following instructions.

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

• "How to disable or enable Windows Me System Restore"
• "How to turn off or turn on Windows XP System Restore"

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. Finding and stopping a 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 svhost.exe and drvrquery32.exe.
6. If you find either of these files, click the filename, and then click End Process.
7. Exit the Task Manager.

3. Finding and stopping the service

1. Click Start, and then click Run.
2. Type services.msc, and then click OK.
3. Locate and select the service, "startupdll."
4. Click Action, and then click Properties.
5. Click Stop.
6. Change Startup Type to Manual.
7. Repeat for the services, "msinet" and "drvmanager."
8. Click OK and close the Services window.
9. Restart the computer.

4. Removing values from the registry

CAUTION: 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 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
   
   Then click OK. (The Registry Editor opens.)
   
   
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
4. In the right pane, delete the values:
   
   drvmanager = c:winntsystem32drvrquery32.exe /S
   HideRun.exe = c:winntsystem32Hiderun.exe c:winntsystem32svhost.exe c:winntsystem32pro.gif
   Xecuter.bat = c:winntsystem32psexec.bat
   
   
5. Exit the Registry Editor.

5. 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.

6. 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 BAT.Boohoo.Worm, Backdoor.Trojan, or Hacktool, click Delete.
4. Refer to the list in the "Technical Details" section and use Windows Explorer to delete any of the non-malicious files that you find in the WinntSystem32 directory.