- April 10, 2005
- February 13, 2007 12:36:45 PM
Also Known As:
- Win32.Mytob.AP [Computer Assoc, Net-Worm.Win32.Mytob.t [Kasper, W32/Mytob.t@MM [McAfee], W32/Mytob-AL [Sophos], WORM_MYTOB.AL [Trend Micro]
- Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP
When W32.Mytob.AJ@mm is executed, it performs the following actions:
- Copies itself as the following:
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).
- Creates a file named C:\sysrun.exe, which is detected as W32.Mytob.L@mm.
- Attempts to send a file named funny_pic.scr to MSN Messenger contacts.
- Adds the value:
"Major Microsoft Windows Driver Boot loader" = "bpool.exe"
to the registry keys:
so that W32.Mytob.AJ@mm runs every time Winodws starts.
Notes: The worm will continuously check for the presence of these registry keys and recreate them if they are deleted.
- Creates a mutex named "H-xxxxxxxxxxxxxxxxE-L-L-B-O-T" so that only one instance of the worm is run on the compromised computer.
- Collects email addresses from the Windows Address Book and from the following locations:
- %Windir%\Temporary Internet Files
- %Userprofile%\Local Settings\Temporary Internet Files
- %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows or C:\Winnt.
- %UserProfile% is a variable that refers to the current user's profile folder. By default, this is C:\Documents and Settings\<Current User> (Windows NT/2000/XP).
- %System% is a variable that refers to the folder that Windows uses to store critical system files. By default, this is C:\Windows\System32 (Windows XP), C:\Winnt\System32 (Windows 2000, NT), or C:\Windows\System (Windows 9x, ME)
- Searches for email addresses in files on drives C through Y that contain the any of the following strings in their extensions:
- The worm then uses its own SMTP engine to send itself to the email addresses that it finds. The email has the following characteristics:
The address contains one of the following names:
followed by one of the following domains:
Note: The worm may also spoof an address from one of those found on the computer.
One of the following:
- One of the following:
- Good Day
- Mail Delivery System
- Mail Transaction Failed
- Server Report
- (random characters)
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.
- The original message was included as an attachment.
- Here are your banks documents
One of the following:
- One of the following:
- [random file name]
with one of the following extensions:
Note: The attachment may have a .zip extension and contain a file with a dual extension. The first extension will be .doc, .htm, or .txt, followed by .exe, .pif, or .scr as the second extension.
The worm avoids sending itself to email addresses that contain any of the following strings:
or contain any of the following domain names:
The worm may append the following prefixes to domain names in an attempt to find Simple Mail Transfer Protocol (SMTP) servers:
- Opens a back door on TCP port 61137.
- Connects to an IRC channel on the shell15.fiberirc.net or shell16.fiberirc.ne domains and listens for commands. This allows the remote attacker to perform any of the following actions:
- Download and execute files
- Perform other IRC commands determined by the attacker
- Restart the compromised computer
- Exploits the following vulnerabilities in order to spread to other computers:
- Blocks access to several security-related Web sites by appending the following text to the Hosts file:
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: Takayoshi Nakayama