W32.Mydoom.B@mm

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Discovered: January 28, 2004
Updated: January 29, 2004 9:04:11 PM
Type: Worm
Infection Length: 29184 and 6144 bytes
Systems Affected: Windows

W32.Mydoom.B@mm is an encrypted mass-mailing worm that arrives as an attachment with either a .exe, .scr, .cmd, .zip, or .pif extension. It also performs a denial of service attack on www.microsoft.com and allows unauthorized remote access to the compromised host.

Antivirus Protection Dates

  • Initial Rapid Release version January 28, 2004
  • Latest Rapid Release version January 15, 2018 revision 020
  • Initial Daily Certified version January 28, 2004
  • Latest Daily Certified version January 15, 2018 revision 024
  • Initial Weekly Certified release date January 28, 2004

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

Writeup By: Scott Gettis

Discovered: January 28, 2004
Updated: January 29, 2004 9:04:11 PM
Type: Worm
Infection Length: 29184 and 6144 bytes
Systems Affected: Windows

W32.Mydoom.B@mm is an encrypted mass-mailing worm that arrives as a message attachment using either a .exe, .scr, .cmd, or .pif extension. These files may be included as an attached .zip archive. The worm sends itself to all email addresses it locates in files on the system with the following extensions:
.htm
.sht
.php
.asp
.dbx
.tbb
.adb
.pl
.wab
.txt

It will avoid sending itself to addresses in any domain names containing the following strings:
avp
syma
icrosof
msn.
hotmail
panda
sopho
borlan
inpris
example
mydomai
nodomai
ruslis
.gov
gov.
.mil
foo.
berkeley
unix
math
bsd
mit.e
gnu
fsf.
ibm.com
google
kernel
linux
fido
usenet
iana
ietf
rfc-ed
sendmail
arin.
ripe.
isi.e
isc.o
secur
acketst
pgp
tanford.e
utgers.ed
mozilla

It also avoids sending itself to any of the following usernames:
root
info
samples
postmaster
webmaster
noone
nobody
nothing
anyone
someone
your
you
me
bugs
rating
site
contact
soft
no
somebody
privacy
service
help
not
submit
feste
ca
gold-certs
the.bat
page
admin
icrosoft
support
ntivi
unix
bsd
linux
listserv
certific
google
accoun

The worm may spoof the From address of the messages it sends. To do so, it takes random addresses it gathered above and adds one of the following usernames to the domain name:
sandra
linda
julie
jimmy
jerry
helen
debby
claudia
brenda
anna
alice
brent
adam
ted
fred
jack
bill
stan
smith
steve
matt
dave
dan
joe
jane
bob
robert
peter
tom
ray
mary
serg
brian
jim
maria
leo
jose
andrew
sam
george
david
kevin
mike
james
michael
alex
john

The message may have the following properties:
Subject may include the following:
Returned mail
Delivery Error
Status
Server Report
Mail Transaction Failed
Mail Delivery System
hello
hi

Message Body can be one of the following:
sendmail daemon reported:
Error #804 occured during SMTP session. Partial message has been received.

Mail transaction failed. Partial message is available.

The message contains Unicode characters and has been sent as a binary attachment.

The message contains MIME-encoded graphics and has been sent as a binary attachment.

The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.

The attachment may be use one of the following filenames:
document
readme
doc
text
file
data
test
message
body

It may also use a double extension. If it does, the first extension will be one the following:
.htm
.txt
.doc

The attachment will always end with one of the following extensions:
.pif
.scr
.exe
.cmd
.bat
.zip

The icon used may be that of a text file if the extension is .exe or .scr, otherwise it uses the icon of an MS-DOS application.

When the attachment is executed, Notepad will open displaying garbage characters from the file %Temp%\Message dropped by the worm.

Next, it creates the following copy of itself:
%System%\explorer.exe

The worm then creates the following registry entries so that it executes every time Windows starts:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run\Explorer = %System%\explorer.exe

HKEY_CURRENT_USER\Software\Microsft\Windows\CurrentVersion\Run\Explorer = %System%\explorer.exe

The worm will also modify the following registry entry so that it will be loaded by explorer.exe:
HKEY_CLASSES_ROOT\CLSID\{E6FB5E20-DE35-11CF-9C87-00AA005127ED}\InProcServer32\"(Default)" = "%System%\ctfmon.dll"

The following registry keys are also created:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\Version

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\Version

The worm also copies itself to the user's Kazaa downloads directory using one of the following filenames:
xsharez_scanner
BlackIce_Firewall_Enterpriseactivation_crack
zapSetup_95_693
MS59-56_hotfix
winamp0
NessusScan_pro
attackXP-6.71

with one of the following extensions:
pif
scr
bat

If the shimgapi.dll file dropped by W32.Novarg.A@mm is present, the worm will delete it. It then drops the following file:
%System%\ctfmon.dll

This file appears to function as a back door that allows remote access to a compromised host on TCP ports 1080, 3128, 80, 8080, or 10080. Evidence suggests that this back door may also allow the compromised system to be used as a remote proxy.

The worm also appears to be capable of performing a denial of service attack on two distinct websites. If the compromised system date is greater than or equal to Feb 1, 2004, the worm will perform a DoS attack on www.sco.com. During the DoS attack, the worm creates 7 threads that invoke GET requests continuously for the main page of www.sco.com.

However, if the compromised system date is greater than or equal to Feb 3, 2004, the worm performs the DoS attack on www.microsoft.com. During this DoS attack, the worm creates 13 threads that invoke GET requests continuously for the main page of www.microsoft.com.

The worm continues its DoS attack until March 1, 2004.

The worm uses the hostname (i.e. www.sco.com and www.microsoft.com) and not a specific IP.

This variant also overwrites the HOSTS file in order to prevent the user from accessing various websites. Some of the websites include antivirus and security vendors, possibly to prevent the user from obtaining antivirus updates and fix tools. The following entries are added to the HOSTS file:
ad.doubleclick.net
ad.fastclick.net
ads.fastclick.net
ar.atwola.com
atdmt.com
avp.ch
avp.com
avp.ru
awaps.net
banner.fastclick.net
banners.fastclick.net
ca.com
click.atdmt.com
clicks.atdmt.com
dispatch.mcafee.com
download.mcafee.com
download.microsoft.com
downloads.microsoft.com
engine.awaps.net
fastclick.net
f-secure.com
ftp.f-secure.com
ftp.sophos.com
go.microsoft.com
liveupdate.symantec.com
mast.mcafee.com
mcafee.com
media.fastclick.net
msdn.microsoft.com
my-etrust.com
nai.com
networkassociates.com
office.microsoft.com
phx.corporate-ir.net
secure.nai.com
securityresponse.symantec.com
service1.symantec.com
sophos.com
spd.atdmt.com
support.microsoft.com
symantec.com
update.symantec.com
updates.symantec.com
us.mcafee.com
vil.nai.com
viruslist.ru
windowsupdate.microsoft.com
www.avp.ch
www.avp.com
www.avp.ru
www.awaps.net
www.ca.com
www.fastclick.net
www.f-secure.com
www.kaspersky.ru
www.mcafee.com
www.microsoft.com
www.my-etrust.com
www.nai.com
www.networkassociates.com
www.sophos.com
www.symantec.com
www.trendmicro.com
www.viruslist.ru
www3.ca.com

UPDATE: It appears that W32.Mydoom.B@mm scans for systems listening on TCP port 3127. This port is associated with the back door installed by W32.Novarg.A@mm (MCID 2468). If the worm finds a Novarg.A system listening on TCP port 3127, it will issue commands to terminate the worm and install Mydoom.B on the system.

*UPDATE: A previous conjecture regarding the possible failure of a denial of service routine targeted against www.microsoft.com, due to HOSTS file modifications has been proven false during ongoing analysis. The denial of service routine is fully functional.

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: Scott Gettis

Discovered: January 28, 2004
Updated: January 29, 2004 9:04:11 PM
Type: Worm
Infection Length: 29184 and 6144 bytes
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.
  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.

    If you use Norton AntiVirus 2006, Symantec AntiVirus Corporate Edition 10.0, or newer products, LiveUpdate definitions are updated daily. These products include newer technology.

    If you use Norton AntiVirus 2005, Symantec AntiVirus Corporate Edition 9.0, or earlier products, LiveUpdate definitions are updated weekly. The exception is major outbreaks, when definitions are updated more often.


  • 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.

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 .

3. To run a full system scan
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.

    For Norton AntiVirus consumer products: Read the document: How to configure Norton AntiVirus to scan all files.

    For Symantec AntiVirus Enterprise products: Read the document: How to verify that a Symantec Corporate antivirus product is set to scan all files.


  2. Run a full system scan.
  3. If any files are detected, follow the instructions displayed by your antivirus program.
Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do 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 the next section.

Warning messages may be displayed when the computer is restarted, since the threat may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [FILE PATH]
Message body: Windows cannot find [FILE NAME]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.

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.

    Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.
  4. Navigate to and delete the following entries:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run\"Explorer" = " %System%\explorer.exe "
    HKEY_CURRENT_USER\Software\Microsft\Windows\CurrentVersion\Run\"Explorer" = " "%System%\explorer.exe"
    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\Version
    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\ComDlg32\Version
    HKEY_CLASSES_ROOT\CLSID\{E6FB5E20-DE35-11CF-9C87-00AA005127ED}\InProcServer32\"(Default)" = "%System%\ctfmon.dll"
  5. Exit the Registry Editor.

Writeup By: Scott Gettis