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What Does W32.Mydoom?

 When W32.Mydoom.A@mm is executed, it does the following:

1. Creates the following files:

• %System%\Shimgapi.dll: Shimgapi.dll acts as a proxy server, opening TCP listening ports in the range of 3127 to 3198. The backdoor also has the ability to download and execute arbitrary files.

• %Temp%\Message: This file contains random letters and is displayed using Notepad.
• %System%\Taskmon.exe.

Notes:

• Taskmon.exe is a legitimate file in the Windows 95/98/Me operating systems, but is in the %Windir% folder, not the %System% folder. (By default, this is C:\Windows or C:\Winnt.) Do not delete the legitimate file in the %Windir% folder.

• %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).

• %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).

2. Adds the value:

 "(Default)" = "%System%\shimgapi.dll" to the registry key:
HKEY_CLASSES_ROOT\CLSID\{E6FB5E20-DE35-11CF-9C87-00AA005127ED}\ InProcServer32 so that Explorer.exe loads Shimgapi.dll.

3. Adds the value:

"TaskMon" = "%System%\taskmon.exe" to the registry keys:

HKEY_CURRENT_USER\Software\Microsft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
so that TaskMon is run when you start Windows.

4. Checks the system date, and if the date is between February 1, 2004 and February 12, 2004, there is a 25% chance the worm will perform a DoS attack against www.sco.com. The DoS is performed by creating 63 new threads that send GET requests and use a direct connection to port 80. The worm will not mass mail itself if the DoS attack is triggered.

Notes:

• The DoS attack will start at 16:09:18 UTC (08:09:18 PST) on February 1, 2004. The worm checks the local system time and date to determine if it should initiate the DoS attack.
• Due to the way the worm verifies the system date, the DoS will only be executed on 25% of infected computers.
• The DoS will only occur when the system date is checked during the initial infection, or if the computer is restarted.
• The worm will use local DNS settings to resolve the domain name used in the DoS attack (www.sco.com).

5. Creates the following registry keys:

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

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

6.Searches for the email addresses in the files with the following extensions:

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

7. Attempts to send email messages using its own SMTP engine. The worm looks up the mail server that the recipient uses before sending the email. If it is unsuccessful, it will use the local mail server instead. The email will have the following characteristics:

From: The "From" address may be spoofed.

Subject: The subject will be one of the following:
test
hi
hello
Mail Delivery System
Mail Transaction Failed
Server Report
Status
Error

Message: The message will be one of the following:
Mail transaction failed. Partial message is available.
The message contains Unicode characters 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.
test

Attachment: The attachment file name, not including the extension, will be one of the following:
document
readme
doc
text
file
data
test
message
body

The attached file may have either one or two file extensions. If it does have two, the first extension will be one of the following:
.htm
.txt
.doc

The second extension, or the only extension if there is only one, will be one of the following:
.pif
.scr
.exe
.cmd
.bat
.zip (This is an actual .zip file that contains a copy of the worm, sharing the same file name as the .zip. For example, readme.zip can contain readme.exe.)

If the worm has an extension of .exe or .scr

For all the other file extensions, it will use the icon for that file type.

8. Copies itself to the Kazaa download folder as one of the following files:

• winamp5
• icq2004-final
• activation_crack
• strip-girl-2.0bdcom_patches
• rootkitXP
• office_crack
• nuke2004
  
  with a file extension of:
• .pif
• .scr
• .bat
• .exe

Removal Instructions

Manual Removal
Perform a manual removal if you cannot obtain the tool.

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines5

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.A@mm.

5. Delete the values that were added to the registry.

6. Reregister the webcheck.dll file. (This will remove the registry modifications responsible for loading Shimgapi.dll.)

Specific Details

1. Disabling 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:

• "How to disable or enable Windows Me System Restore"
• "How to turn off or turn on Windows XP System Restore"

Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable 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. Updating 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 Virus Definitions (LiveUpdate).
• 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. Restarting 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. Scanning for and deleting the infected files

• 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."
• Run a full system scan.
• If any files are detected as infected with W32.Mydoom.A@mm, click Delete.

5. Deleting the values from the registry

Note: %System% is a variable that refers to the location of 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).

5. Exit the Registry Editor.

6. Reregistering the Webcheck.dll file
(This will remove the registry modifications responsible for loading Shimgapi.dll.)

1. Click Start, and then click Run. (The Run dialog box appears.)
2. Type, or copy and paste, the following text:
   regsvr32 webcheck.dll

Click OK. When you see the message, "DllRegisterServer in webcheck.dll
succeeded," click OK.

Geri...