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


Risk Level 2: Low

March 14, 2005
February 13, 2007 12:35:21 PM
Also Known As:
Win32.Mytob.H [Computer Associ, Net-Worm.Win32.Mytob.d [Kasper, W32/Mydoom.gen@MM [McAfee], W32/MyDoom-Gen [Sophos], WORM_MYTOB.H [Trend Micro]
Systems Affected:

When W32.Mytob.E@mm is executed, it performs the following actions:
  1. Creates the following copies of itself:

    • %System%\taskgmr.exe
    • %System%\winnett.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. Adds the value:

    "SVCHOST" = "taskgmr.exe"

    to the registry subkeys:


    so that it runs every time Windows starts.

  3. Gathers email addresses from the Windows Address Book and from files with the following extensions:

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

      The worm will ignore email addresses that contain any of the following strings:

    • -._!
    • -._!@
    • .edu
    • .gov
    • .mil
    • abuse
    • accoun
    • acketst
    • admin
    • anyone
    • arin.
    • avp
    • be_loyal:
    • berkeley
    • borlan
    • bsd
    • bugs
    • ca
    • certific
    • contact
    • example
    • spam
    • feste
    • fido
    • foo.
    • fsf.
    • gnu
    • gold-certs
    • google
    • gov.
    • help
    • hotmail
    • iana
    • ibm.com
    • icrosof
    • icrosoft
    • ietf
    • info
    • inpris
    • isc.o
    • isi.e
    • kernel
    • linux
    • listserv
    • math
    • me
    • mit.e
    • mozilla
    • msn.
    • 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
    • spm
    • submit
    • support
    • syma
    • tanford.e
    • the.bat
    • unix
    • usenet
    • utgers.ed
    • webmaster
    • www
    • you
    • your

      The worm may also add one of the following names to domain names gathered from the compromised computer to generate email addresses:

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

  4. Appends the following prefixes to domain names in an attempt to find Simple Mail Transfer Protocol (SMTP) servers:

    • gate.
    • ns.
    • relay.
    • mail1.
    • mxs.
    • mx1.
    • smtp.
    • mail.
    • mx.

  5. Uses its own SMTP engine to send itself to the email addresses that it finds. The email has the following characteristics:

    From: Spoofed

    One of the following:

    • hello
    • God day
    • Error
    • Status
    • Mail Transaction Failed
    • Mail Delivery System
    • Server Report
    • (No Subject)
    • (random letters)

      One of the following:

    • The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.
    • Mail transaction failed. Partial message is available.
    • The message contains Unicode characters and has been sent as a binary attachment.
    • The original message was included as an attachment.
    • Here are your banks documents.
    • The original message was included as an attachment.
    • (No body)
    • (Random data)

      The attachment may contain one of the following file names:

    • body
    • data
    • doc
    • document
    • file
    • message
    • readme
    • test
    • text
    • (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

  6. Connects to an IRC channel on the bleh.darkacidonline.us domain on TCP port 8080. The worm listens for commands that allow the remote attacker to perform the following actions:

    • Download files
    • Execute files
    • Delete files
    • Update itself
    • Get uptime information

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

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


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: Ka Chun Leung
Summary| Technical Details| Removal

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