W32.Mytob.O@mm

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Discovered: March 25, 2005
Updated: February 13, 2007 12:35:48 PM
Also Known As: Net-Worm.Win32.Mytob.h [Kasper, W32/Mytob.gen@MM [McAfee]
Type: Worm
Systems Affected: Windows



W32.Mytob.O@mm is a mass-mailing worm with back door capabilities. The worm uses its own SMTP engine to send email to addresses that it gathers from the compromised computer. The worm also spreads by exploiting the Microsoft Windows Local Security Authority Service Remote Buffer Overflow (as described in Microsoft Security Bulletin MS04-011 ).



Removing entries from the Hosts file
If this threat has modified the Windows Hosts file, there are two ways to remove these entries:

  • Install and run the current version of LiveUpdate. This will remove only the entries that refer to Symantec domains.
  • Manually edit the Hosts file and remove all the entries that the threat added.

To run the current version of LiveUpdate
  1. Click download LiveUpdate.

    Note:
    If you are not reading this Web page on the computer that is getting the error notice, the address for downloading the file is:

    ftp://ftp.symantec.com/public/english_us_canada/liveupdate/lusetup.exe

    If necessary, you can type this address into the address bar of the problem computer. Changes to the Hosts file will not stop you from getting to this site.

  2. Save the file to the Windows desktop.
  3. Double-click the lusetup.exe icon on the desktop to install LiveUpdate.
  4. Run LiveUpdate.
  5. Did you see the message "LU1860: LiveUpdate has detected a potential security compromise on your computer"?
    • If you did, let LiveUpdate "Remove these entries from the hosts files" (Recommended).
      This should allow LiveUpdate to run.
    • If you did not, that was not the cause of the problem. Return to the Removal section.


To manually edit the Hosts file and remove all the entries that the worm added

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 Hosts file that you find, right-click the file, and then click Open With.
    6. Deselect the "Always use this program to open this program" check box.
    7. Scroll through the list of programs and double-click Notepad.
    8. When the file opens, delete all the entries in step ten of the "Technical Details" section.
    9. Close Notepad and save your changes when prompted.

  • Windows XP
    1. Click Start > 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 Hosts file that you find, right-click the file, and then click Open With.
    11. Deselect the Always use this program to open this program check box.
    12. Scroll through the list of programs and double-click Notepad.
    13. When the file opens, delete all the entries in step ten of the "Technical Details" section.
    14. Close Notepad and save your changes when prompted.


Antivirus Protection Dates

  • Initial Rapid Release version March 25, 2005
  • Latest Rapid Release version March 25, 2005
  • Initial Daily Certified version March 25, 2005
  • Latest Daily Certified version March 25, 2005
  • Initial Weekly Certified release date March 25, 2005

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

Writeup By: Candid Wueest

Discovered: March 25, 2005
Updated: February 13, 2007 12:35:48 PM
Also Known As: Net-Worm.Win32.Mytob.h [Kasper, W32/Mytob.gen@MM [McAfee]
Type: Worm
Systems Affected: Windows


When W32.Mytob.O@mm is executed, it performs the following actions:

  1. Copies itself as %System%\taskgmr.exe

    Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  2. Drops the file %SystemDrive%\hellmsn.exe which then creates the following copies of the worm:

    • %SystemDrive%\funny_pic.scr
    • %SystemDrive%\my_photo2005.scr
    • %SystemDrive%\see_this!!.scr

      Note: %SystemDrive% is a variable that refers to the drive on which Windows is installed. By default, this is drive C.

  3. Adds the value:

    "WINTASK" = "taskgmr.exe"

    to the registry subkeys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
    RunServices
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\SYSTEM\CurrentControlSet\Control\Lsa
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
    HKEY_CURRENT_USER\Software\Microsoft\OLE
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\OLE

    so that it runs every time Windows starts.

    Note: The worm will continuously check for the presence of these registry keys and recreate them if they are deleted.

  4. Gathers email addresses from the Windows Address Book and from the following folders:

    • %Windir%\Temporary Internet Files
    • %Userprofile%\Local Settings\Temporary Internet Files

      Notes:
    • %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows or C:\Winnt.
    • %UserProfile% is a variable that refers to the current user's profile folder. By default, this is C:\Documents and Settings\<Current User> (Windows NT/2000/XP).

  5. Searches for email addresses in files on fixed and RAM drives with the following strings in their extensions:

    • .adb*
    • .asp*
    • .dbx*
    • .htm*
    • .php*
    • .pl
    • .sht*
    • .tbb*
    • .wab*

      Note: If the worm searches for the .htm* string, the search will return .htm and .html files.

      The worm will not send itself to email addresses that contain any of the following strings:

    • .gov
    • .mil
    • accoun
    • acketst
    • admin
    • anyone
    • arin.
    • avp
    • berkeley
    • borlan
    • bsd
    • bugs
    • ca
    • certific
    • contact
    • example
    • feste
    • fido
    • foo.
    • fsf.
    • gnu
    • gold-certs
    • google
    • gov.
    • help
    • iana
    • ibm.com
    • icrosof
    • icrosoft
    • ietf
    • info
    • inpris
    • isc.o
    • isi.e
    • kernel
    • linux
    • listserv
    • math
    • me
    • mit.e
    • mozilla
    • mydomai
    • no
    • nobody
    • nodomai
    • noone
    • not
    • nothing
    • ntivi
    • page
    • panda
    • pgp
    • postmaster
    • privacy
    • rating
    • rfc-ed
    • ripe.
    • root
    • ruslis
    • samples
    • secur
    • sendmail
    • service
    • site
    • soft
    • somebody
    • someone
    • sopho
    • submit
    • support
    • syma
    • tanford.e
    • the.bat
    • unix
    • usenet
    • utgers.ed
    • webmaster
    • you
    • your

  6. The worm then uses its own SMTP engine to send itself to the email addresses that it finds. The email has the following characteristics:

    From:
    One of the following names:

    • adam
    • alex
    • andrew
    • anna
    • bill
    • bob
    • brenda
    • brent
    • brian
    • britney
    • bush
    • claudia
    • dan
    • dave
    • david
    • debby
    • fred
    • george
    • helen
    • jack
    • james
    • jane
    • jerry
    • jim
    • jimmy
    • joe
    • john
    • jose
    • julie
    • kevin
    • leo
    • linda
    • lolita
    • madmax
    • maria
    • mary
    • matt
    • michael
    • mike
    • peter
    • ray
    • robert
    • sam
    • sandra
    • serg
    • smith
    • stan
    • steve
    • ted
    • tom

      followed by one of these domains:

    • aol.com
    • cia.gov
    • fbi.gov
    • hotmail.com
    • juno.com
    • msn.com
    • yahoo.com


      Subject:
      One of the following:

    • Good day
    • hello
    • Mail Delivery System
    • Mail Transaction Failed
    • Server Report
    • Status
    • Error
    • [No Subject]
    • [random letters]


      Message:
      One of the following:

    • Here are your banks documents.
    • The original message was included as an attachments.
    • The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.
    • The message contains Unicode characters and has been sent as a binary attachment.
    • Mail transaction failed. Partial message is available.
    • [Random data]


      Attachment:
      One of the following:

    • document
    • readme
    • doc
    • text
    • file
    • data
    • test
    • message
    • body
    • [random letters]

      with one of the following extensions:

    • .bat
    • .cmd
    • .exe
    • .pif
    • .scr
    • .zip

      If the attachment is a .zip file, the copy of the worm may have one of the following second extensions:

    • .doc
    • .txt
    • .htm
    • .html

  7. Loads an FTP server, which runs on a random TCP port.

  8. Connects to a predetermined IRC channel on the d66.myleftnut.info domain and listens for commands. The commands will allow the remote attacker to perform the following actions:

    • Download and execute files
    • Restart the computer
    • Perform other IRC commands determined by the remote attacker

  9. Scans for vulnerable computers and tries to exploit the Microsoft Windows Local Security Authority Service Remote Buffer Overflow (as described in Microsoft Security Bulletin MS04-011).

  10. Blocks access to several security-related Web sites by appending the following text to the Hosts file:
    127.0.0.1   www.symantec.com
    127.0.0.1   securityresponse.symantec.com
    127.0.0.1   symantec.com
    127.0.0.1   www.sophos.com
    127.0.0.1   sophos.com
    127.0.0.1   www.mcafee.com
    127.0.0.1   mcafee.com
    127.0.0.1   liveupdate.symantecliveupdate.com
    127.0.0.1   www.viruslist.com
    127.0.0.1   viruslist.com
    127.0.0.1   viruslist.com
    127.0.0.1   f-secure.com
    127.0.0.1   www.f-secure.com
    127.0.0.1   kaspersky.com
    127.0.0.1   www.avp.com
    127.0.0.1   www.kaspersky.com
    127.0.0.1   avp.com
    127.0.0.1   www.networkassociates.com
    127.0.0.1   networkassociates.com
    127.0.0.1   www.ca.com
    127.0.0.1   ca.com
    127.0.0.1   mast.mcafee.com
    127.0.0.1   my-etrust.com
    127.0.0.1   www.my-etrust.com
    127.0.0.1   download.mcafee.com
    127.0.0.1   dispatch.mcafee.com
    127.0.0.1   secure.nai.com
    127.0.0.1   nai.com
    127.0.0.1   www.nai.com
    127.0.0.1   update.symantec.com
    127.0.0.1   updates.symantec.com
    127.0.0.1   us.mcafee.com
    127.0.0.1   liveupdate.symantec.com
    127.0.0.1   customer.symantec.com
    127.0.0.1   rads.mcafee.com
    127.0.0.1   trendmicro.com
    127.0.0.1   www.microsoft.com
    127.0.0.1   www.trendmicro.com


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: Candid Wueest

Discovered: March 25, 2005
Updated: February 13, 2007 12:35:48 PM
Also Known As: Net-Worm.Win32.Mytob.h [Kasper, W32/Mytob.gen@MM [McAfee]
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.Mytob.O@mm.
  4. Delete any values 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, reenable 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 document: 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 document: Virus Definitions (Intelligent Updater).

    The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.

    Note: If you see an error, such as LU1418, when you try to run LiveUpdate and you cannot get the Web site hosting the Intelligent Updater, it is likely that the worm has modified the Hosts file. You can either download and install LiveUpdate 2.5, which can remove Symantec entries from that file, or you can edit it yourself. See the instructions for both in the "Additional Information" section below.

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.Mytob.O@mm, click Delete.

    Note:
    If your Symantec antivirus product reports that it cannot delete an infected file, Windows may be using the file. To fix this, run the scan in Safe mode. For instructions, read the document: How to start the computer in Safe Mode. Once you have restarted in Safe mode, run the scan again.

    After the files are deleted, restart the computer in Normal mode and proceed with section 4.

4. To delete the value 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 subkeys only. For instructions refer to the document: How to make a backup of the Windows registry.
  1. Click Start > Run.
  2. Type regedit
  3. Click OK.

  4. Navigate to the subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
    RunServices
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\SYSTEM\CurrentControlSet\Control\Lsa
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
    HKEY_CURRENT_USER\Software\Microsoft\OLE
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\OLE

  5. In the right pane, delete the value:

    "WINTASK" = "taskgmr.exe"

  6. Exit the Registry Editor.


Writeup By: Candid Wueest