W32.Remadmin

SUMMARY

W32.Remadmin is a worm that attempts to propagate through network shares.

Behavior

Symptoms

Transmission

Protection

• Virus Definitions (LiveUpdate™ Weekly) September 8, 2004
• Virus Definitions (Intelligent Updater) September 3, 2004

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
• Degrades Performance: Generates heavy network traffic by establishing and scanning network shares.

Distribution

• Distribution Level: Low
• Shared Drives: Establishes network shares and attempts to copy itself.

TECHNICAL DETAILS

W32.Remadmin is composed of batch files, hacktools, and legitimate administration tools.

When the worm is executed, it does the following:

1. Extracts the following files:
   
   • AdmDll.dll (A DLL component of Remacc.Radmin.)
   • icon.reg (A registry file.)*
   • Kcah.cmd (A batch file that copies utili.dll to <IP address>ADMIN$SYSTEM32 and attempts to stop certain processes.)
   • Msdos.exe (An .exe file that is detected as Remacc.Radmin.)
   • Msxml3b.dll (A clean text file with a list of I.D.s.)*
   • Msxml4b.dll (A clean text file with a list of passwords.)*
   • Naer.cmd (A batch file that calls Kcah.cmd with a specified IP address, excluding 192.168.0.x and 127.0.0.x.)
   • Psexec.exe (A Sysinternals remote execution tool.)*
   • Raddrv.dll (A DLL component of Remacc.Radmin.)
   • Regedit4.exe (A registry editor.)*
   • Rs.cmd (A batch file that calls msdos.exe.)*
   • Run.bat (A starting batch file for the worm.)
   • Secfind.exe (A hacktool used to search for IPC$ shares.)
   • Secscan.exe (An .exe file that is detected as Hacktool.RunService.)
   • Star.cmd (A batch file that calls Kcah.cmd with random IP address.)
   • Unrar.exe
     This is a RAR archive containing the following:
     • i.cmd (A starting batch file that stops/removes netsvc.exe and overwrites files.)
     • instsrv.exe (A service installer.)*
     • Regedit4.exe (A registry editor.)*
     • Rep.exe (A non-malicious program called Replace Commander, which is used to replace specific strings in a file.)*
     • S.bin (A clean file used to overwrite a copy of %SystemRoot%System32 etsvc.exe.)*
     • V.bin (A clean file used to overwrite %SystemRoot%.{21EC2020-3AEA-1069-A2DD-08002B-30309D} etsvc.exe.)*
     • W.exe (A clean file used to overwrite %SystemRoot%.{21EC2020-3AEA-1069-A2DD-08002B-30309D} etsvc.ini.)*
       
       NOTE: Files that marked with an asterisk ( * ) are either commercial utilities or are clean files. As such, Symantec antivirus products do not detect them.
       
       
2. Creates the registry key:
   
   HKEY_LOCAL_MACHINESystemRAdmin
   
   
3. Executes Run.bat which:
   
   • Copies Rar.exe to Utili.dll
   • Executes Star.cmd, which does the following:
     • Executes Secfind.exe with a range of IP address to search for IPC$ shares.
     • Executes Kcah.cmd and Naer.cmd and copies Utili.dll into <IP address>ADMIN$SYSTEM32Rar.exe and stops certain processes.
     • Executes Rar.exe.
   • Executes Unrar.exe to stop Netsvc.exe and overwrite the following files:
     • Copies v.bin to %SystemRoot%.{21EC2020-3AEA-1069-A2DD-08002B-30309D} etsvc.exe
     • Copies w.exe to %SystemRoot%.{21EC2020-3AEA-1069-A2DD-08002B-30309D} etsvc.ini
     • Copies s.bin to %SystemRoot%System32 etsvc.exe
   • May create one or more user accounts in the administrators group, also adding the account to the following local groups:
     • administratoren
     • administrators
     • administrateurs
   • Creates the following administrative shares:
     • IPC$
     • ADMIN$
     • C$=C:
       
       
4. Executes Star.cmd, which starts the following services:
   
   • RemoteRegistry
   • NetBios
   • TlntSvr (Telnet)
   • TermServ

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. Update the virus definitions.
2. Restart the computer in Safe mode or VGA mode.
3. Run a full system scan and delete all the files detected as W32.Remadmin.
4. Delete the values that were added to the registry.
   

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

1. To update 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 daily. 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. To restart the computer in Safe mode or VGA mode

Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.

• For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
• For Windows NT 4 users, restart the computer in VGA mode.

3. To scan for and delete 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 W32.Remadmin, click Delete.

4. To delete the values 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 keys only. Read the document, "How to make a backup of the Windows registry," for instructions.

1. Click Start > Run.
2. Type regedit
   
   Then click OK.
   
3. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESystem
   
4. In the left pane, delete the key:
   
   "RAdmin"
   
5. Exit the Registry Editor.
   
   
6. Restart the computer in normal mode.