W32.Mytob.JW@mm

SUMMARY

W32.Mytob.JW@mm is a mass-mailing worm that opens a back door and lowers security settings on the compromised computer.

Protection

• Virus Definitions (LiveUpdate™ Weekly) October 5, 2005
• Virus Definitions (Intelligent Updater) October 3, 2005

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Medium
• Payload: Opens a back door that allows a remote attacker to have unauthorized access to the compromised computer.
• Large Scale E-mailing: Creates a mass-mailing of itself which may impact system performance.
• Degrades Performance: Creates a mass-mailing of itself, which may clog mail servers or degrade network performance.

Distribution

• Distribution Level: Low
• Subject of Email: Varies
• Name of Attachment: Varies
• Ports: TCP ports 10027, 8000

TECHNICAL DETAILS

When W32.Mytob.JW@mm is executed it performs the following actions:

1. Creates the following copy of itself:
   
   %System% askman.exe
   
   Note: %System% is a variable that refers to the System folder. By default this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   
   
2. Creates the following files, which are also copies of itself:
   
   
   • C:funny_pic.scr
   • C:my_photo2005.scr
   • C:see_this!!.scr
     
     
3. Creates the file C:hellmsn.exe, which is a copy of W32.Mytob.L@mm and sends a copy of one of the following files to all MSN Messenger contacts:
   
   
   • funny_pic.scr
   • my_photo2005.scr
   • see_this!!.scr
     
     
4. Adds the value:
   
   "WINTASKMAN" = "taskman.exe"
   
   to the registry subkeys:
   
   HKEY_CURRENT_USERSoftwareMicrosoftOLE
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun
   HKEY_CURRENT_USERSYSTEMCurrentControlSetControlLsa
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftOLE
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunServices
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlLsa
   
   so that it runs when Windows starts.
   
   
5. Creates the following mutex so that only one instance of the worm is run on the compromised computer:
   
   H-E-L-L-B-O-T
   
   
6. Gathers email addresses from the Windows Address Book and from files with the following extensions:
   
   
   • .wab
   • .adb
   • .tbb
   • .dbx
   • .asp
   • .php
   • .sht
   • .htm
     
     
7. Will not send itself to email addresses that contain any of the following strings:
   
   
   • .edu
   • .gov
   • .mil
   • abuse
   • accoun
   • acketst
   • admin
   • anyone
   • arin.
   • avp
   • berkeley
   • borlan
   • bsd
   • bugs
   • certific
   • contact
   • example
   • feste
   • fido
   • foo.
   • fsf.
   • gnu
   • gold-certs
   • google
   • gov.
   • help
   • iana
   • ibm.com
   • icrosof
   • icrosoft
   • ietf
   • info
   • inpris
   • isc.o
   • isi.e
   • kernel
   • linux
   • listserv
   • math
   • mit.e
   • mozilla
   • 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
   • submit
   • support
   • syma
   • tanford.e
   • the.bat
   • unix
   • usenet
   • utgers.ed
   • webmaster
   • www
   • you
   • your
     
     
8. Checks for valid SMTP servers by prepending one of the following strings to the gathered addresses:
   
   
   • mx
   • mail
   • smtp
   • mx1
   • mxs
   • mail1
   • relay
   • ns
   • gate
     
     
9. Uses its own SMTP engine to send itself to the email addresses that it finds.
   The email has the following characteristics:
   
   From:
   One of the following:
   
   
   • adam
   • alex
   • andrew
   • anna
   • bill
   • bob
   • brenda
   • brent
   • brian
   • claudia
   • dan
   • dave
   • david
   • debby
   • frank
   • fred
   • george
   • helen
   • jack
   • james
   • jane
   • jerry
   • jim
   • jimmy
   • joe
   • john
   • jose
   • josh
   • julie
   • kevin
   • leo
   • linda
   • maria
   • mary
   • matt
   • michael
   • mike
   • paul
   • peter
   • ray
   • robert
   • sales
   • sam
   • sandra
   • serg
   • smith
   • stan
   • steve
   • ted
   • tom
     
     Subject:
     One of the following:
     
     
   • Good day
   • hello
   • Mail Delivery System
   • Mail Transaction Failed
   • Server Report
   • Status
   • Error
     
     Message:
     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.
   • [RANDOM]
     
     Attachment:
     One of the following:
     
     
   • body
   • data
   • document
   • doc
   • file
   • text
   • test
   • message
   • readme
     
     The attachment is a .zip file, the copy of the worm may have one of the following second extensions:
     
     
   • .doc
   • .txt
   • .htm
   • .tmp
     
     
10. Connects to a predertermined Web site on TCP port 8000 and waits for commands from a remote attacker to perform any of the following actions:
    
    
    • Execute files
    • Download files
    • Perform other IRC commands determined by the remote attacker
      
      
11. Creates an FTP server, which runs on a random TCP port.
    
    
12. Attempts to exploit the Microsoft Windows Local Security Authority Service Remote Buffer Overflow vulnerability (as described in Microsoft Security Bulletin MS04-011) in order to spread to other vulnerable computers.
    
    
13. Drops a file named 2pac.txt if it successfully compromises a new computer.
    
    
14. Opens TCP port 10027 and downloads a copy of the worm as bingoo.exe.
    
    
15. Blocks access to several security-related Web sites by appending the following text to the hosts file:
    
    127.0.0.1 www.symantec.com
    127.0.0.1 securityresponse.symantec.com
    127.0.0.1 symantec.com
    127.0.0.1 www.sophos.com
    127.0.0.1 sophos.com
    127.0.0.1 www.mcafee.com
    127.0.0.1 mcafee.com
    127.0.0.1 liveupdate.symantecliveupdate.com
    127.0.0.1 www.viruslist.com
    127.0.0.1 viruslist.com
    127.0.0.1 viruslist.com
    127.0.0.1 f-secure.com
    127.0.0.1 www.f-secure.com
    127.0.0.1 kaspersky.com
    127.0.0.1 www.avp.com
    127.0.0.1 www.kaspersky.com
    127.0.0.1 avp.com
    127.0.0.1 www.networkassociates.com
    127.0.0.1 networkassociates.com
    127.0.0.1 www.ca.com
    127.0.0.1 ca.com
    127.0.0.1 mast.mcafee.com
    127.0.0.1 my-etrust.com
    127.0.0.1 www.my-etrust.com
    127.0.0.1 download.mcafee.com
    127.0.0.1 dispatch.mcafee.com
    127.0.0.1 secure.nai.com
    127.0.0.1 nai.com
    127.0.0.1 www.nai.com
    127.0.0.1 update.symantec.com
    127.0.0.1 updates.symantec.com
    127.0.0.1 us.mcafee.com
    127.0.0.1 liveupdate.symantec.com
    127.0.0.1 customer.symantec.com
    127.0.0.1 rads.mcafee.com
    127.0.0.1 trendmicro.com
    127.0.0.1 www.microsoft.com
    127.0.0.1 www.trendmicro.com
    

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

REMOVAL

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. Remove all the entries that the risk added to the hosts file
3. Update the virus definitions.
4. Run a full system scan and delete all the files detected.
5. 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:

• 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, 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 remove all the entries that the risk added to the hosts file

1. Navigate to the following location:
   
   
   • Windows 95/98/Me:
     %Windir%
   • Windows NT/2000/XP:
     %Windir%System32driversetc
     
     Notes:
   • The location of the hosts file may vary and some computers may not have this file. There may also be multiple copies of this file in different locations. If the file is not located in these folders, search your disk drives for the hosts file, and then complete the following steps for each instance found.
   • %Windir% is a variable that refers to the Windows installation folder. By default, this is C:Windows (Windows 95/98/Me/XP) or C:Winnt (Windows NT/2000).
     
     
2. Double-click the hosts file.
3. If necessary, deselect the "Always use this program to open this program" check box.
4. Scroll through the list of programs and double-click Notepad.
5. When the file opens, delete all the entries added by the risk. (See the Technical Details section for a complete list of entries.)
6. Close Notepad and save your changes when prompted.
   

3. 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: 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 Virus Definitions (LiveUpdate).
• 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. To determine whether definitions for this threat are available by the Intelligent Updater, refer to Virus Definitions (Intelligent Updater).
  
  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.

4. To scan for and delete the infected files

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, click Delete.

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.


5. 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 the subkey:
   
   HKEY_CURRENT_USERSoftwareMicrosoftOLE
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun
   HKEY_CURRENT_USERSYSTEMCurrentControlSetControlLsa
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftOLE
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunServices
   HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlLsa
   
   
5. In the right pane, delete the value:
   
   "WINTASKMAN" = "taskman.exe"
   
   
6. Exit the Registry Editor.