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Discovered: May 27, 1998
Updated: February 13, 2007 11:57:34 AM
Also Known As: Remote Explorer, W32.IE403R, WinNT.RemEx
Type: Virus

This virus targets the Windows NT environment. It infects executable files on the infected computer and attached network drives.

Antivirus Protection Dates

  • Initial Rapid Release version May 28, 1998
  • Latest Rapid Release version May 28, 1998
  • Initial Daily Certified version May 28, 1998
  • Latest Daily Certified version May 28, 1998

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

Writeup By: Raul Elnitiarta

Discovered: May 27, 1998
Updated: February 13, 2007 11:57:34 AM
Also Known As: Remote Explorer, W32.IE403R, WinNT.RemEx
Type: Virus

If a user with administrator privileges executes an infected program, the virus installs itself as the service "Remote Explorer." The virus-installed service resides on the infected system as \WinNT\System32\drivers\ie403r.sys. On weekdays between 6 A.M. and 3 P.M., the virus sets its thread priority to the lowest setting. On weekdays between 3 P.M. and 6 A.M. and on weekends, the virus sets its thread priority to one step above the lowest setting. Thus the virus becomes more active during "off-work" hours. This service also creates the Taskmgr.sys process approximately every 10 minutes.

The virus can infect files on attached network drives over a Windows NT network, provided that another Windows NT computer that has an identical admin-user logon to it is logged on to the infected computer when the viral-service is running. When activated, the infection routine picks a folder at random on the shared network drive. It proceeds to infect the .exe files in the chosen folder, and except for files with the extensions .dll or .tmp, it encrypts the remaining files. In infecting .exe files, the virus does not check if the file is Win32 or not; thus, some DOS .exe files will be infected. The infection adds 150 KB of code.

When infecting a Win32 .exe file (host), the virus adds the host's icon(s) to the infected file's ICON resource section, and it adds the GZIP-compressed host program into the infected file's RCDATA resource section. The infected file also carries a GZIP-compressed of Psapi.dll and a GZIP-compressed copy of the viral service module (IE403R.SYS) in its RCDATA resource section. The GZIP-compressed host is extracted into a temporary folder, and when an infected file is executed; the virus passes control to the extracted host after it runs its viral code.

The virus does not work on other Windows platforms. In Windows 95, executing an infected file will give an error message about a missing .dll export. In Windows 98, executing an infected file will execute the host file but does not install the Windows NT-specific viral service.


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.

Writeup By: Raul Elnitiarta

Discovered: May 27, 1998
Updated: February 13, 2007 11:57:34 AM
Also Known As: Remote Explorer, W32.IE403R, WinNT.RemEx
Type: Virus

Once infected, the best way to remove this virus is to use the Reremove.exe removal tool . Please click here for more information.

To disinfect a Windows 95/98 computer on which files are infected with W32.RemoteExplore:
Windows 95/98 computers can host files infected with the W32.RemoteExplore virus, but it cannot spread under Windows 95/98.

  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
  3. If any files are detected as infected by W32.RemoteExplore, click Repair.

Manual removal procedure
  1. Determine whether the computer is infected by viewing TaskMgr for Remote Explorer under Processes, or under Control Panel/Services. If it is not, stop here. Otherwise, go on to the next step.

    CAUTION: We strongly recommend that you back up the system registry before making any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure you modify only the keys specified. Please see the document How to back up the Windows registry before proceeding.
  2. Click Start, and click Run. The Run dialog box appears.
  3. Type regedit and then click OK. The Registry Editor opens.
  4. Delete the following keys:

  5. Restart the computer.
  6. Delete the following files:

  7. Run a full system scan. If any files cannot be repaired, they will have to be restored from clean backups.

Writeup By: Raul Elnitiarta