Trojan.Norio

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Discovered: September 04, 2003
Updated: February 13, 2007 12:23:36 PM
Also Known As: TrojanDownloader.Win32.Small.b, Downloader-EA [McAfee]
Type: Trojan Horse
Systems Affected: Windows


Trojan.Norio is a Trojan horse that modifies browser and network settings to direct you to pornographic Web sites. This Trojan horse changes the default Explorer home page and search pages by modifying the registry.

The worm includes a component that can download and execute arbitrary code on your computer.


Note: At the time of this writing, this Trojan uses the file names, Winupdate.exe and Lookupsys.exe, in the Windows folder.


Antivirus Protection Dates

  • Initial Rapid Release version September 04, 2003
  • Latest Rapid Release version March 23, 2017 revision 037
  • Initial Daily Certified version September 04, 2003
  • Latest Daily Certified version March 23, 2017 revision 041
  • Initial Weekly Certified release date September 04, 2003

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

Writeup By: Heather Shannon

Discovered: September 04, 2003
Updated: February 13, 2007 12:23:36 PM
Also Known As: TrojanDownloader.Win32.Small.b, Downloader-EA [McAfee]
Type: Trojan Horse
Systems Affected: Windows


When Trojan.Norio is executed, it does the following:

  1. Adds at least one of the following values:

    "Windows Update"="<file name>"
    "service"="<file name> delete"
    "service_ls"="<file name> delete"
    "Network Service"="<file name> -sr -0"

    to the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

  2. Creates the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\WinUpdate

    which is used to store a unique identification number.

  3. Adds entries to one of the files, %Windir%\Hosts or %Windir%\System32\drivers\etc\Hosts.
    These entries may redirect the following URLs to point to the local computer, which may result in error messages when you try to access them:

    www.coolwebsearch.org
    coolwebsearch.org
    www.coolwebsearch.info
    coolwebsearch.info
    www.searchcomplete.com
    searchcomplete.com
    www.coolsearcher.net
    coolsearcher.net
    www.adulthyperlinks.com
    adulthyperlinks.com
    www.allhyperlinks.com
    allhyperlinks.com
    www.white-pages.ws
    white-pages.ws
    www.clearsearch.net
    clearsearch.net
    www.youfindall.net
    youfindall.net
    www.coolwwwsearch.com
    coolwwwsearch.com
    www.unipages.cc
    unipages.cc
    www.sexy18.cc
    sexy18.cc
    www.trafficswitcher.com
    trafficswitcher.com
    www.trafficback.com
    trafficback.com
    www.selfbookmark.com
    selfbookmark.com

  4. Modifies the value for:

    "SearchURL"

    in the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer

  5. Modifies the values for:

    "Search Page"
    "Search Bar"

    in the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main

  6. Modifies the values for:

    "Default_Search_URL"
    "Search Page"

    in the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main

  7. Modifies the values for:

    "SearchAssistant"

    in the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Search

  8. Modifies the values for:

    "SearchAssistant"
    "CustomizeSearch"

    in the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Search

  9. Monitors open Web browser windows. If the title of an open Web page contains strings that the Trojan determines are characteristic of a porn site, it will open another porn site in a new browser window.

  10. Periodically contacts a Web server for instructions. The response contains the URL for a file, which the Trojan will download and execute. This functionality may be used to update the Trojan or run any other code on a compromised system.

  11. The Trojan may delete itself when the computer restarts.


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.

Writeup By: Heather Shannon

Discovered: September 04, 2003
Updated: February 13, 2007 12:23:36 PM
Also Known As: TrojanDownloader.Win32.Small.b, Downloader-EA [McAfee]
Type: Trojan Horse
Systems Affected: Windows



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. Update the virus definitions.
  3. Run a full system scan and delete all the files detected as Trojan.Norio.
  4. Reverse the changes to the registry.
  5. Remove the entries that were added to the Hosts file.
  6. Reset the Internet Explorer home page.
  7. Reset the Internet Explorer search pages.
For specific details on each of these steps, read the following instructions.

1. To disable 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:
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. 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 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.

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.
  2. Run a full system scan.
  3. If any files are detected as infected with Trojan.Norio, write down the file names, and click Delete.

4. To reverse the changes to the registry


WARNING: 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

    and then click OK. (The Registry Editor opens.)

  3. Navigate to the key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

  4. In the right pane, delete any of these values, or any values that refer to the file names, which were detected as Trojan.Norio:

    "Windows Update"="<file name>"
    "service"="<file name> delete"
    "service_ls"="<file name> delete"
    "Network Service"="<file name> -sr -0"

  5. Navigate to and delete the key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\WinUpdate

  6. Exit the Registry Editor.

5. To remove the entries from the Hosts file

Note: The location of the Hosts file may vary, and some computers may not have this file.

For example, if the file exists in Windows 98, it will usually be in C:\Windows; and it is located in the C:\WINNT\system32\drivers\etc folder in Windows 2000. There may also be multiple copies of this file in different locations.

Follow the instructions for your operating system:
  • Windows 95/98/Me/NT/2000
    1. Click Start, point to Find or Search, and then click Files or Folders.
    2. Make sure that "Look in" is set to (C:) and that "Include subfolders" is checked.
    3. In the "Named" or "Search for..." box, type:

      hosts

    4. Click Find Now or Search Now.
    5. For each one that you find, note its location. (This is displayed in the "In Folder" column.)
    6. Right-click each Hosts file, and then click "Open With."
    7. Deselect the "Always use this program to open this program" check box.
    8. Scroll through the list of programs and double-click Notepad.
    9. When the file opens,delete all the entries in the Hosts file, except for the following line:

      127.0.0.1     localhost

    10. Close Notepad and save your changes when prompted.

  • Windows XP
    1. Click Start, and then click Search.
    2. Click All files and folders.
    3. In the "All or part of the file name" box, type:

      hosts

    4. Verify that "Look in" is set to "Local Hard Drives" or to (C:).
    5. Click "More advanced options."
    6. Check "Search system folders."
    7. Check "Search subfolders."
    8. Click Search.
    9. Click Find Now or Search Now.
    10. For each one that you find, note its location. (This is displayed in the "In Folder" column.)
    11. Right-click each Hosts file, and then click "Open With."
    12. Deselect the "Always use this program to open this program" check box.
    13. Scroll through the list of programs and double-click Notepad.
    14. delete all the entries in the Hosts file, except for the following line:

      127.0.0.1     localhost

    15. Close Notepad and save your changes when prompted.
6. To reset the Internet Explorer home page
  1. Start Microsoft Internet Explorer.
  2. Connect to the Internet, and then go to the page that you want to set as your home page.
  3. Click the Tools menu > Internet Options.
  4. In the Home page section of the General tab, click Use Current, and then click OK.

For additional information, or if this procedure does not work, read the Microsoft® Knowledge Base article, "Home Page Setting Changes Unexpectedly, or You Cannot Change Your Home Page Setting, Article ID 320159 ."
    7. To reset the Internet Explorer Search pages
    Follow the instructions for your version of Windows.

    Windows 98/Me/2000
    1. Start Microsoft Internet Explorer.
    2. Click the Search button on the toolbar.
    3. In the Search pane, click Customize.
    4. Click Reset.
    5. Click Autosearch Settings.
    6. Select a search site from the drop-down list, and then click OK.
    7. Click OK.

    Windows XP
    Because Windows XP is set by default to use animated characters in the search, how you perform this procedure can vary. Read all the instructions before you start.
    1. Start Microsoft Internet Explorer.
    2. Click the Search button on the toolbar.
    3. Do one of the following:
      • If the pane that opens looks similar to this picture:





        click the word Customize. Then skip to step h.

      • If the pane that opens has the words "Search Companion" at the top, and the center looks similar to this picture:






        click the "Change preferences" link as shown above. Then proceed with step d.

    4. Click the "Change Internet search behavior" link.
    5. Under "Internet Search Behavior," click "With Classic Internet Search."
    6. Click OK. Then close Internet Explorer. (Close the program for the change to take effect.)
    7. Start Internet Explorer. When the search pane opens, it should now look similar to this:





      Click the word Customize, and then go on to the next step.

    8. In the Search pane, click Customize.
    9. Click Reset.
    10. Click Autosearch Settings.
    11. Select a search site from the drop-down list, and then click OK.
    12. Click OK.
    13. Do one of the following:
      • If you were using (or want to continue using) the "Classic Internet Search" panel, stop here (or proceed with the next section).
      • If you want to go back to the "Search Companion" search (it usually has an animated character at the button), proceed with step n.

    14. Click the word Customize again.
    15. In the "Customize Search Settings" window, click "Use Search Companion," and then click OK.
    16. Close Internet Explorer. The next time that you open it, it will use the Search Companion again.


    Writeup By: Heather Shannon