W32.Netsky.N@mm

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Discovered: March 16, 2004
Updated: February 13, 2007 12:19:09 PM
Also Known As: W32/Netsky.n@MM [McAfee], I-Worm.NetSky.o [Kaspersky]
Type: Worm
Systems Affected: Windows


W32.Netsky.N@mm is a mass-mailing worm that uses its own SMTP engine to send itself to the email addresses it finds when scanning the hard drives and mapped drives.

The "sender" of the email is spoofed, and its subject, message body, and attachment vary. The attachment has a .pif extension.

This threat is compressed with tELock.


Note: The worm has an MD5 hash value of 0xDD4D58534FA472E4735A532D15A6547F.


Antivirus Protection Dates

  • Initial Rapid Release version March 17, 2004
  • Latest Rapid Release version September 13, 2017 revision 019
  • Initial Daily Certified version March 17, 2004
  • Latest Daily Certified version September 14, 2017 revision 004
  • Initial Weekly Certified release date March 17, 2004

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

Writeup By: Kevin Ha

Discovered: March 16, 2004
Updated: February 13, 2007 12:19:09 PM
Also Known As: W32/Netsky.n@MM [McAfee], I-Worm.NetSky.o [Kaspersky]
Type: Worm
Systems Affected: Windows


When W32.Netsky.N@mm runs, it does the following:

  1. Creates a mutex named "NetDy_Mutex_Psycho". This mutex allows only one instance of the worm to execute.

  2. Copies itself as %Windir%\VisualGuard.exe.

  3. Creates the following files:
    • %Windir%\base64.tmp (46,308 bytes): MIME-encoded version of the executable
    • %Windir%\zip1.tmp (46,478 bytes): MIME-encoded version of worm in zip archive
    • %Windir%\zip2.tmp (46,490 bytes): MIME-encoded version of worm in zip archive
    • %Windir%\zip3.tmp (46,464 bytes): MIME-encoded version of worm in zip archive
    • %Windir%\zip4.tmp (46,646 bytes): MIME-encoded version of worm in zip archive
    • %Windir%\zip5.tmp (46,658 bytes): MIME-encoded version of worm in zip archive
    • %Windir%\zip6.tmp (46,670 bytes): MIME-encoded version of worm in zip archive
    • %Windir%\zipped.tmp (34,054 bytes): Worm in zip archive

  4. Adds the value:

    "NetDy"="%Windir%\VisualGuard.exe"

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    so that the worm runs when you start Windows.

  5. Deletes the values:
    • DELETE ME
    • Explorer
    • msgsvr32
    • Sentry
    • service
    • system.
    • Taskmon
    • Windows Services Host

      from the registry key:

      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

  6. Deletes the values:
    • au.exe
    • d3dupdate.exe
    • gouday.exe
    • OLE
    • rate.exe
    • srate.exe
    • ssate.exe
    • sysmon.exe
    • Taskmon
    • Windows Services Host

      from the registry key:

      HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

  7. Deletes the following subkeys:
    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\PINF
    • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WksPatch
    • HKEY_CLASSES_ROOT\CLSID\CLSID\{E6FB5E20-DE35-11CF-9C87-00AA005127ED}\InProcServer32

  8. Retrieves the email addresses from the files that have these extensions:
    • .adb
    • .asp
    • .cgi
    • .dbx
    • .dhtm
    • .doc
    • .eml
    • .htm
    • .html
    • .jsp
    • .msg
    • .oft
    • .php
    • .pl
    • .rtf
    • .sht
    • .shtm
    • .tbb
    • .txt
    • .uin
    • .vbs
    • .wab
    • .wsh
    • .xml


      Note: Due to a bug in the code, the worm will search a file for email addresses if the extension is a sub-string of one of the aforementioned extensions.

      For example, the worm will scan the files with the .txt, .tx, and .t extensions.

  9. Uses its own SMTP engine to send itself to the email addresses it finds. The worm uses the local DNS server (retrieved using an API call), if available, to perform an MX lookup for the recipient address.

  10. The email has the following characteristics:

    From: <Spoofed>

    Subject: The subject line is composed of multiple parts.
    • The first part may be one of the following:
      • Re:
      • Re: Re:
    • The second part may be one of the following:
      • my
      • your
      • [blank]
    • The third part may be one of the following:
      • application
      • approved
      • approved
      • bill
      • corrected
      • data
      • details
      • document
      • document_all
      • excel document
      • file
      • hello
      • here
      • hi
      • important
      • important
      • improved
      • information
      • letter
      • message
      • patched
      • product
      • read it immediately
      • screensaver
      • text
      • thanks!
      • website
      • word document
    Message:
      • The message is one of the following:
        • Authentication required.
        • I have attached your document.
        • I have received your document. The corrected document is attached.
        • Please confirm the document.
        • Please read the attached file.
        • Please read the document.
        • Please read the important document.
        • Please see the attached file for details.
        • Requested file.
        • See the file.
        • Your details.
        • Your document is attached to this mail.
        • Your document is attached.
        • Your document.
        • Your file is attached.
      • Followed by:
        --------------------------------------------
        (attachment_name) : No virus found
        Powered by the new Norton OnlineScan
        Get protected: www.symantec.com
    Attachment: The attachment is one of the following with a .zip, .pif, .exe, or .scr extension:
    • application_%s
    • approved_%s
    • bill_%s
    • data_%s
    • details_%s
    • document_%s
    • document_all_%s
    • excel document_%s
    • file_%s
    • important_%s
    • information_%s
    • letter_%s
    • message_%s
    • product_%s
    • screensaver_%s
    • text_%s
    • website_%s
    • word document_%s
    where %s is the portion of the "To" address before the "@".


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: Kevin Ha

Discovered: March 16, 2004
Updated: February 13, 2007 12:19:09 PM
Also Known As: W32/Netsky.n@MM [McAfee], I-Worm.NetSky.o [Kaspersky]
Type: Worm
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 W32.Netsky.N@mm.
  4. Delete the value that was added to the registry.
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:
Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

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 W32.Netsky.N@mm, click Delete.

4. To delete the value from 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

    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 the value:

    "NetDy"="%Windir%\VisualGuard.exe"

  5. Exit the Registry Editor.


Writeup By: Kevin Ha