1. Symantec/
  2. Security Response/
  3. W32.Mydoom.F@mm

W32.Mydoom.F@mm

Risk Level 2: Low

Discovered:
February 20, 2004
Updated:
February 13, 2007 12:17:50 PM
Also Known As:
W32/Mydoom.f@MM [McAfee], WORM_MYDOOM.F [Trend], W32/MyDoom-F [Sophos], I-Worm.Mydoom.f [Kaspersky], Win32.Mydoom.F [Computer Assoc
Type:
Worm
Systems Affected:
Windows

When W32.Mydoom.F@mm is executed, it does the following:
  1. Creates a mutex, "jmydoat<the infected computer name>Xmtx," which allows only one instance of the worm to execute in memory.

  2. May display a fake message:

    Title: Error
    Text: (One of the following)
    • File is corrupted
    • File cannot be opened
    • Unable to open specified file

  3. May create a file in the %Temp% folder that contains randomly generated data if it does not display the above message. The worm opens the file with notepad.exe. This behavior is identical to those of previous W32.Mydoom variants.


    Note: %Temp% is a variable. The worm locates the temporary folder and copies itself to that location. By default, this is C:\Windows\TEMP (Windows 95/98/Me), or C:\WINNT\Temp (Windows NT/2000), or C:\Document and Settings\<UserName>\Local Settings\Temp (Windows XP).

  4. Copies itself to the %System% folder using a randomly generated file name, made up of four to 13 lower case letters with a .exe extension.


    Note: %System% is a variable: The worm locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  5. Creates a .dll file in the %System% folder using a randomly generated file name, made up of four to eight lower case letters, with randomly generated data appended to the end of the .dll file.

  6. Opens a backdoor listening on TCP port 1080, using the .dll component, which acts as a proxy server and can also download and execute the arbitrary files.

  7. Terminates any processes whose name contains one of the following strings:
    • reged
    • taskmo
    • taskmg
    • avp.
    • avp32
    • norton
    • navapw
    • navw3
    • intrena
    • mcafe

  8. Iterates through all the drives (hard drive, remote drive, or RAM drive), C through Z, creates randomly named copies of itself as .exe to randomly selected folders, or creates its .zip archive files using randomly generated file names.


    Notes:
    • The size of the .exe file is 34,568 bytes.
    • The size of the .zip file is 34K.

  9. Adds the value:

    "<four to eight random, lowercase letters>" = "%System%\<the filename of the worm>"

    to one of the registry keys:
    • HKEY_CURRENT_USER\Software\Microsft\Windows\CurrentVersion\
      Run
    • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\
      Run


      so that the worm runs when you restart Windows.

  10. Creates the following registry keys:
    • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\
      Shell
    • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\
      Shell

  11. Checks the local system date. If the date is between the 17th and 22nd of any month, there is a 68% chance the worm will perform a DoS attack against www.microsoft.com, and a 32% chance of a DoS attack against www.riaa.com. The DoS is performed by creating random numbers of new threads that send GET requests and use a direct connection to port 80.

  12. Searches the folders on drives C to Z for the files with the following extensions:
    • .mdb
    • .doc
    • .xls
    • .sav
    • .jpg
    • .avi
    • .bmp

  13. If the drive is a hard drive, remote drive, or RAM drive, the worm randomly deletes the files it finds with the following probability:
    • .mdb - 98%
    • .doc - 40%
    • .xls - 60%
    • .sav - 95%
    • .jpg - 8%
    • .avi - 10%
    • .bmp - 15%

  14. Searches the folders on drives C to Z for the files with the following extensions, and for any files whose names contain "Inbox."
    • .wab
    • .mbx
    • .nch
    • .mmf
    • .ods
    • .rtf
    • .uin
    • .oft
    • .mht
    • .vbs
    • .msg
    • .pl
    • .eml
    • .adb
    • .tbb
    • .dbx
    • .asp
    • .php
    • .sht
    • .htm
    • .txt

  15. If the drive is a hard drive, remote drive, or RAM drive, the worm will retrieve the email addresses from the files it finds.

  16. Retrieves the email addresses from the %TemporaryInternetFiles% folder and the Windows address book.


    Note: %TemporaryInternetFiles% is a variable. The worm locates the Temporary Internet Files folder and copies itself to that location. By default, this is C:\Windows\Temporary Internet Files (Windows 95/98/Me), or C:\Document and Settings\<UserName>\Local Settings\Temporary Internet Files (Windows NT/2000/XP).

  17. The worm avoids the email addresses that contain the following strings:
    • mozilla
    • utgers.ed
    • tanford.e
    • fsf.
    • gnu
    • mit.e
    • bsd
    • math
    • unix
    • berkeley
    • ripe.
    • arin.
    • sendmail
    • rfc-ed
    • ietf
    • iana
    • irix
    • solaris
    • sgi.com
    • sun.com
    • slashdot
    • sourcef
    • usenet
    • fido
    • linux
    • kernel
    • google
    • ibm.com
    • pgp
    • acketst
    • secur
    • isc.o
    • isi.e
    • nai.co
    • essagela
    • suppo
    • foo.
    • .mil
    • gov.
    • .gov
    • ruslis
    • nodoma
    • mydoma
    • example
    • inpris
    • borlan
    • sopho
    • panda
    • hotmail
    • msn.
    • icrosof
    • syma

  18. Uses its own engine to send itself, or its .zip archive, to the email addresses it finds. The email has the following characteristics:

    From:
    The senders name may be one of the following:
    • jerry
    • bill
    • smith
    • jim
    • sam
    • james
    • alex
    • <random characters>

      with one of the following domains:

    • aol.com
    • msn.com
    • yahoo.com
    • hotmail.com
    • <random characters.edu>


      Note: The worm may also use the email addresses it finds from the local files.


      Subject: (One of the following)
    • <blank>
    • Announcement
    • Re: Thank you
    • Thank you
    • Re: Details
    • Details
    • Re: Approved
    • Approved
    • hi, it's me
    • Thank You very very much
    • You use illegal File Sharing...
    • Your IP was logged
    • Your account is about to be expired
    • Love is
    • Love is...
    • Undeliverable message
    • Re: <censored>
    • Your order was registered
    • Your request was registered
    • Your order is being processed
    • Your request is being processed
    • Current Status
    • read now!
    • forget
    • bug
    • unknown
    • fake
    • Wanted
    • recent news
    • news
    • stolen
    • Attention
    • Accident
    • Schedule
    • Your credit card
    • Read it immediately!
    • Read this
    • Read it immediately
    • Something for you
    • For you
    • For your information
    • Information
    • Warning
    • You have 1 day left
    • automatic notification
    • automatic responder
    • Notification
    • Expired account
    • Your account has expired
    • Important
    • Readme
    • Read this message
    • please read
    • please reply
    • Registration confirmation
    • Confirmation
    • Confirmation Required
    • Returned Mail
    • hello
    • hi


      Message: (One of the following)
    • You are bad
    • Take it
    • Reply
    • Please, reply
    • Information about you
    • Greetings
    • See you
    • Here it is
    • We have received this document from your e-mail.
    • Kill the writer of this document!
    • Something about you
    • I have your password :)
    • You are a bad writer
    • Is that yours?
    • Is that from you?
    • I wait for your reply.
    • Here is the document.
    • Read the details.
    • I'm waiting
    • Okay
    • OK
    • Everything ok?
    • Check the attached document.
    • The document was sent in compressed format.
    • Please see the attached file for details
    • See the attached file for details
    • Details are in the attached document. You need Microsoft Office to open it.


      Attachment: (One of the following)
    • photo
    • resume
    • image
    • your_document
    • approved
    • paypal
    • disc
    • misc
    • part3
    • part2
    • part4
    • part1
    • mail2
    • object
    • website
    • friend
    • jokes
    • joke
    • list
    • mail
    • story
    • about
    • money
    • check
    • product
    • notes
    • note
    • information
    • textfile
    • posting
    • post
    • stuff
    • attachment
    • creditcard
    • details
    • body
    • message
    • test
    • data
    • file
    • text
    • readme
    • document
    • doc
    • msg
    • <some randomly letters>

      with one of the following extensions:
    • .exe
    • .scr
    • .com
    • .pif
    • .bat
    • .cmd


      The attached file may have two extensions. If it does have two, the first extension will be one of the following:
    • .doc
    • .htm
    • .rtf
    • .xls
    • .jpg
    • .gif
    • .png
    • .txt

      followed by 40 to 159 spaces.

      The second extension will be one of the following:
    • .exe
    • .pif
    • .scr


      Notes:
    • There is a 40% chance that the worm may send a .zip file as an attachment. This is an actual .zip file that contains a copy of the worm, sharing the same file name as the .zip. (For example, details.zip can contain detail.exe.)
    • If the worm has an extension of .exe or .scr, the file will be displayed with the following icon:





      For all the other file extensions, it will use the icon for that file type.
Symantec Firewall/VPN 100/200 Appliances

By default, Symantec's stateful inspection firewall technology protects against the propagation of the W32.Mydoom.F@mm worm, by blocking attackers from accessing the TCP/1080 backdoor port on infected systems. Administrators are urged to verify that their security policy has not been modified to allow TCP/1080 inbound.

Symantec Gateway Security 5400 Series and Symantec Gateway Security v1.0
  • Antivirus component: An update for the Symantec Gateway Security AntiVirus engine to protect against the W32.Mydoom.F@mm is now available. Symantec Gateway Security users are advised to run LiveUpdate.
  • Full application inspection firewall component: By default, Symantec's full application inspection firewall technology protects against the propagation of the W32.Mydoom.F@mm worm by blocking attackers from accessing the TCP port 1080 backdoor on infected computers. Administrators are urged to verify that their security policies have not been modified to allow TCP port 1080 inbound.

Symantec Enterprise Firewall 7.0.x and Symantec VelociRaptor 1.5
By default, Symantec's full application inspection firewall technology protects against the propagation of the W32.Mydoom.F@mm worm by blocking attackers from accessing the TCP port 1080 backdoor on infected computers. Administrators are urged to verify that their security policies have not been modified to allow TCP port 1080 inbound.

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: Yana Liu
Summary| Technical Details| Removal

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