W32.Frethem.J@mm is a worm, and is a variant of W32.Frethem.B@mm. It uses its own SMTP engine to send itself to email addresses that it finds in the Microsoft Windows Address Book and in .dbx, .wab, .mbx, .eml, and .mdb files.

Wild:

• Number of infections: 0 - 49
• Number of sites: 3 - 9
• Geographical distribution: Low
• Threat containment: Easy
• Removal: Easy

Damage:

• Payload - Large scale e-mailing:
  Sends to email addresses found in the Windows Address Book and .dbx .wab, .mbx, .eml, and .mdb files.

Distribution:

• Subject of email: Re: Your password!
  Name of attachment: decrypt-password.exe , password.txt
  Size of attachment: 47,616 bytes

When this worm is executed, it does the following:

It will copy itself to the file %Windows%\taskbar.exe and configure itself to start with Windows by adding the value:

Task Bar

"%Windows%\taskbar.exe"

to the registry key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

The worm obtains the computer user's SMTP server, email address, and SMTP server name from the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\00000001\SMTP Server

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\00000001\SMTP Email Address

HKEY_CURRENT_USER\Software\Microsoft\
Internet Account Manager\Accounts\00000001\SMTP Display Name

The worm then obtains email addresses from the Microsoft Windows Address Book and from .dbx, .wab, .mbx, .eml, and .mdb files files, and sends itself to those addresses. The email message has the following characteristics:

Subject: Re: Your password!

Message:
ATTENTION!

You can access
very important
information by
this password

DO NOT SAVE
password to disk
use your mind

now press
cancel

Attachments:
Decrypt-password.exe
Password.txt

NOTE: The Decrypt-password.exe attachment is a copy of the worm. It is packed with UPX and PE-Pack, and its size is approximately 46 KB. The second attachment, Password.txt, is a text file that is approximately 93 bytes in length. Password.txt is not viral by itself as such, it is not detected by Norton AntiVirus. However, if the computer was infected by W32.Frethem.J@mm worm, you should delete the file manually.

When the worm arrives by email, it uses both an IFRAME exploit and a MIME exploit, which allow the virus to be executed when you read or even preview the file. Information and a patch for MIME exploit can be found at http://www.microsoft.com/technet/security/bulletin/MS01-020.asp.

The worm creates the "IEXPLORE_MUTEX_AABBCCDDEEFF" mutex. This mutex allows only one instance of the worm to execute in memory.

After sleeping for several hours, the worm copies itself to C:\Windows\All Users\Start Menu\Programs\Startup\Setup.exe so that it is executed each time that you start Windows.

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.
• 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

To remove this worm, update the virus definitions, run a full system scan, and delete all files that are detected as W32.Frethem.J@mm. For details on how to do this, read the following instructions.

1. Update the virus definitions, run a full system scan. Delete all files that are detected as W32.Frethem.J@mm.
2. Delete the value

Task Bar

from the registry key

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

1. To scan with Norton AntiVirus and delete the infected files:
2. Obtain the most recent virus definitions. There are two ways to do this:
• Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
• Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
  
  Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.
  
3. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files.
• NAV Consumer products: Read the document How to configure Norton AntiVirus to scan all files.
• NAV Enterprise products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
4. Run a full system scan.
5. Delete all files that are detected as W32.Frethem.J@mm.

NOTE: If NAV reports that it cannot delete an infected file because it is in use by Windows, you must shut down the computer, turn off the power, and wait 30 seconds. Then restart the computer in Safe mode and run the scan again. All Windows 32-bit operating systems except Windows NT can be restarted in Safe mode. Read the document for your operating system.
• How to start Windows XP in Safe Mode.
• How to start Windows 2000 in Safe mode.
• How to restart Windows 9x or Windows Me in Safe Mode.

To remove the value from the registry:

CAUTION: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to the following key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

4. In the right pane, delete the following value:

Task Bar

5. Click Registry, and click Exit.