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Discovered: July 29, 2004
Updated: February 13, 2007 12:25:56 PM
Type: Worm
Systems Affected: Windows

W32.Mydoom.N@mm is a variant of W32.Mydoom.M@mm. It is a mass-mailing worm that drops and executes a backdoor that is detected as Backdoor.Zincite.A , which listens on TCP port 1034.

The worm uses its own SMTP engine to send itself to email addresses that it finds on the infected computer. The email contains a spoofed From address. The subject and body text will vary, as will the name of the attachment.

This threat is packed using ASPack.

Antivirus Protection Dates

  • Initial Rapid Release version July 29, 2004
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version July 29, 2004
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date August 04, 2004

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

Writeup By: Yana Liu

Discovered: July 29, 2004
Updated: February 13, 2007 12:25:56 PM
Type: Worm
Systems Affected: Windows

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

  1. Creates one of the following registry keys, which mark the computer as infected:

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

    Note: %Windir% is a variable. The worm locates the Windows® installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.
  3. Drops and executes %Windir%\Services.exe, which is detected as Backdoor.Zincite.A.
    When Services.exe runs, it opens TCP port 1034 and listens for remote connections. The backdoor also probes random IP addresses on port 1034 looking for other infected hosts.
  4. Adds the following values:

    "Services" = "%Windir%\services.exe"
    "JavaVM" = "%Windir%\java.exe"

    to one of the following registry keys:


    so that the worm and backdoor load when Windows starts.
  5. May create the following files for logging purposes:
    • %Temp%\Zincite.log
    • %Temp%\<randomly named file>.log
  6. Gathers email addresses from files that have the following extensions:
    • .adb
    • .asp
    • .dbx
    • .ht*
    • .php
    • .pl
    • .sht
    • .tbb
    • .tx*
    • .wab
  7. Queries the following search engines to harvest additional email addresses for possible distribution:
    • search.lycos.com
    • search.yahoo.com
    • www.altavista.com
    • www.google.com
  8. When the worm finds an open Microsoft® Outlook window, it attempts to send itself to the email addresses that it found. The email message has the following characteristics:

    The From address is spoofed.

    Subject: (One of the following)
    • hello
    • hi
    • error
    • status
    • test
    • report
    • delivery failed
    • Message could not be delivered
    • Mail System Error - Returned Mail
    • Delivery reports about your e-mail
    • Returned mail: see transcript for details
    • Returned mail: Data format error
    The content that is contained in the body of the email message varies, based on a number of text options. One of each of the phrases or words in brackets, separated by a "|" character, appears in the following messages:
    • Dear user {<recipient's email address>|of <recipient's email domain>},{ {{M|m}ail {system|server} administrator|administration} of <recipient's email domain> would like to {inform you{ that{:|,}|}|let you know {that|the following}{.|:|,}}|||||}
      {We have {detected|found|received reports} that y|Y}our {e{-|}mail |}account {has been|was} used to send a {large|huge} amount of {{unsolicited{ commercial|}|junk} e{-|}mail|spam}{ messages|} during {this|the {last|recent}} week.
      {We suspect that|Probably,|Most likely|Obviously,} your computer {had been|was} {compromised|infected{ by a recent v{iru}s|}} and now {run|contain}s a {trojan{ed|}|hidden} proxy server.
      {Please|We recommend {that you|you to}} follow {our |the |}instruction{s|} {in the {attachment|attached {text |}file} |}in order to keep your computer safe.
      {{Virtually|Sincerely} yours|Best {wishe|regard}s|Have a nice day},
      {<recipient's email domain> {user |technical |}support team.|The <recipient's email domain> {support |}team.}
    • {The|This|Your} message was{ undeliverable| not delivered} due to the following reason{(s)|}:
      Your message {was not|could not be} delivered because the destination {computer|server} was
      {not |un}reachable within the allowed queue period. The amount of time
      a message is queued before it is returned depends on local configuration parameters.
      Most likely there is a network problem that prevented delivery, but
      it is also possible that the computer is turned off, or does not
      have a mail system running right now.
      Your message {was not|could not be} delivered within <random number> days:
      {{{Mail s|S}erver}|Host} <host used to send the email>} is not responding.
      The following recipients {did|could} not receive this message:
      <<recipient's email address>>
      Please reply to postmaster@{<sender's email domain>|<recipient's email domain>}
      if you feel this message to be in error.
    • The original message was received at [current time]{
      | }from {<sender's email domain> ]|{<host used to send the email>]|]}}
      ----- The following addresses had permanent fatal errors -----
      {<<recipient's email address>>|<recipient's email address>}
      {----- Transcript of {the ||}session follows -----
      ... while talking to {host |{mail |}server ||||}{<recipient's email domain>.|<host used to send the email>]}:
      {>>> MAIL F{rom|ROM}:[From address of mail]
      <<< 50$d {[From address of mail]... |}{Refused|{Access d|D}enied|{User|Domain|Address} {unknown|blacklisted}}|554 <<recipient's email address>>... {Mail quota exceeded|Message is too
      554 <<recipient's email address>>... Service unavailable|550 5.1.2 <<recipient's email address>>... Host unknown (Name server: host not found)|554 {5.0.0 |}Service unavailable; ] blocked using {relays.osirusoft.com|bl.spamcop.net}{, reason: Blocked|}
      Session aborted{, reason: lost connection|}|>>> RCPT To:<<recipient's email address>>
      <<< 550 {MAILBOX NOT FOUND|5.1.1 <<recipient's email address>>... {User unknown|Invalid recipient|Not known here}}|>>> DATA
      {<<< 400-aturner; %MAIL-E-OPENOUT, error opening !AS as output
      |}{<<< 400-aturner; -RMS-E-CRE, ACP file create failed
      |}{<<< 400-aturner; -SYSTEM-F-EXDISKQUOTA, disk quota exceeded
      |}<<< 400}|}
    • The original message was included as attachment
    • {{The|Your} m|M}essage could not be delivered
    • <recipient's email address> is the email address of the person receiving the email.
    • <recipient's email domain> is the domain of the receiver's email. For instance, if the email address is john_doe@example.com, the domain is "example.com."
    • <sender's email domain> is the domain of the sender's email. For instance, if the email address is john_doe@example.com, the domain is "example.com."
    • <host used to send the email> is name of the email server used by the infected computer. The worm gathers this information from the infected computer's registry.
    The worm may generate a file name from a domain name of an email address that is gathered from the computer. For instance, if the worm finds the address john_doe@example.com on the infected computer, the attachment name could contain example.com.

    The attachment name may also be one of the following:
    • readme
    • instruction
    • transcript
    • mail
    • letter
    • file
    • text
    • attachment
    • document
    • message
    with one of the following extensions:
    • .cmd
    • .bat
    • .com
    • .exe
    • .pif
    • .scr
    • .zip
    The attachment may have a second extension, which will be one of the following:
    • doc
    • txt
    • htm
    • html
    • Approximately 30% of the time, the attachment will be zipped. In these cases the attachment may be compressed several times over.
    • There is a 15% chance that the worm will attach a small junk file to the message instead of a copy of itself.
    The worm will not send itself to addresses that contain the following strings:
    • mailer-d
    • spam
    • abuse
    • master
    • sample
    • accou
    • privacycertific
    • bugs
    • listserv
    • submit
    • ntivi
    • support
    • admin
    • page
    • the.bat
    • gold-certs
    • feste
    • not
    • help
    • foo
    • soft
    • site
    • rating
    • you
    • your
    • someone
    • anyone
    • nothing
    • nobody
    • noone
    • info
    • winrar
    • winzip
    • rarsoft
    • sf.net
    • sourceforge
    • ripe.
    • arin.
    • google
    • gnu.
    • gmail
    • seclist
    • secur
    • bar.
    • foo.com
    • trend
    • update
    • uslis
    • domain
    • example
    • sophos
    • yahoo
    • spersk
    • panda
    • hotmail
    • msn.
    • msdn.
    • microsoft
    • sarc.
    • syma
    • avp


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

Discovered: July 29, 2004
Updated: February 13, 2007 12:25:56 PM
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. Restart the computer in Safe mode or VGA mode.
  4. Run a full system scan and delete all the files detected as W32.Mydoom.N@mm.
  5. Reverse the changes made to the registry.
For 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:

When you have completed the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the previously mentioned 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:

  • By 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).
  • By 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 restart the computer in Safe mode or VGA mode

Shut down the computer, and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
  • For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document How to start the computer in Safe Mode.
  • For Windows NT 4 users, restart the computer in VGA mode.
4. 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.Mydoom.N@mm or Backdoor.Zincite.A, click Delete.

5. To reverse the changes made to the registry

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 only the specified keys. Read the document How to make a backup of the Windows registry for instructions.
  1. On the Windows taskbar, click Start > Run.
  2. Type the following:

  3. Click OK.
  4. Select each of the following keys:


    and, in the right pane, delete the following values if they exist:

    "Services" = "%Windir%\services.exe"
    "JavaVM" = "%Windir%\java.exe"
  5. Delete the following keys:

  6. Exit the Registry Editor.
  7. Restart the computer in Normal mode.
    For instructions, read the section on returning to Normal mode in the document How to start the computer in Safe Mode.

Writeup By: Yana Liu