- March 28, 2005
- February 13, 2007 12:35:58 PM
Also Known As:
- Net-Worm.Win32.Mytob.n [Kasper, W32/Mytob.gen@MM [McAfee], WORM_MYTOB.S [Trend Micro]
- Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP
When W32.Mytob.R@mm is executed, it performs the following actions:
- Copies itself as:
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).
- Drops the file %SystemDrive%\hellmsn.exe which then creates the following copies of the worm:
- C:\funny pic.scr
- C:\photo album.scr
- C:\eminem vs 2pac.scr
Note: %SystemDrive% is a variable that refers to the drive on which Windows is installed. By default, this is drive C.
- Adds the value:
"WINTASK" = "taskgmr.exe"
to the registry subkeys:
so that it runs every time Windows starts.
Note: The worm will continuously check for the presence of these registry keys and recreate them if they are deleted.
- The worm creates the following mutex so that only one instance of the worm is run on the compromised computer:
- Gathers email addresses from the Windows Address Book and from the following folders:
- %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).
Searches for email addresses in files on fixed and RAM drives with the following strings in their extensions:
Note: If the worm searches for the .htm* string, the search will return .htm and .html files.
Avoids email addresses that contain any of the following strings:
- Appends domain names to the following prefixes in an attempt to find Simple Mail Transfer Protocol (SMTP) servers:
- Uses its own SMTP engine to send itself to the email addresses that it finds. The email has the following characteristics:
One of the following names:
followed by one of these domains:
One of the following:
- Good day
- Mail Delivery System
- Mail Transaction Failed
- Server Report
One of the following:
- Here are your banks documents.
- The original message was included as an attachments.
- The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment.
- The message contains Unicode characters and has been sent as a binary attachment.
- Mail transaction failed. Partial message is available.
One of the following:
with one of the following extensions:
If the attachment is a .zip file, the copy of the worm may have one of the following second extensions:
- Loads an FTP server, which runs on a random TCP port.
- Connects to a predetermined IRC channel on the irc.blackcarder.net or diablo.corsforcors.com domains and listens for commands. The commands will allow the remote attacker to perform the following actions:
- Download and execute files
- Restart the computer
- Perform other IRC commands determined by the remote attacker
- Exploits the following vulnerabilities in order to spread to other vulnerable computers:
- Microsoft Windows Local Security Authority Service Remote Buffer Overflow (as described in Microsoft Security Bulletin MS04-011).
- Microsoft Windows DCOM RPC Interface Buffer Overrun Vulnerability (as described in Microsoft Security Bulletin MS03-026).
If the worm successfully exploits a vulnerable computer, it may drop a file named 2pac.txt on to the newly compromised computer. This file opens TCP port 10087 and downloads a copy of the worm as bingoo.exe.
- Blocks access to several security-related Web sites by appending the following text to the Hosts file:
- Scan for shared folders with the following weak passwords.
- If the worm successfully finds a shared folder with weak password, the worm may drop one of the following files:
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: Masaki Suenaga