W32.Assarm@mm

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Discovered: August 02, 2002
Updated: February 13, 2007 11:56:08 AM
Type: Worm
Systems Affected: Windows


W32.Assarm@mm is a mass-mailing worm that sends messages in reply to all unread messages in the Microsoft Outlook Mailbox. The email messages are not sent if the day of the week is Monday or Thursday and the hour of the time of day is greater than 5. For example, if the time is 4:00 A.M or 4:00 P.M., the message will be sent; if the time is 6:00 A.M or 6:00 P.M., it will not be sent.

The subject of the email message is "Re: <original message subject line>." The attachment varies.

Antivirus Protection Dates

  • Initial Rapid Release version August 02, 2002
  • Latest Rapid Release version December 31, 2008 revision 037
  • Initial Daily Certified version August 02, 2002
  • Latest Daily Certified version December 31, 2008 revision 041
  • Initial Weekly Certified release date August 07, 2002

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Douglas Knowles

Discovered: August 02, 2002
Updated: February 13, 2007 11:56:08 AM
Type: Worm
Systems Affected: Windows


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

It determines whether the current file name is %windir%\Svchost.exe. If it is, the worm then determines whether the argument "Install Me!" was not passed to it. If both conditions are true, the worm registers itself as a system process.

Next, the worm sends messages in reply to all unread messages in the Microsoft Outlook Mailbox. The email messages are not sent if the day of the week is Monday or Thursday and the hour of the time of day is greater than 5. For example, if the time is 4:00 A.M or 4:00 P.M., the mail will be sent; if the time is 6:00 A.M or 6:00 P.M., it will not be sent. The email message has the following characteristics:

Subject: Re: <original message subject line>
Message:
<infected computer's user name> wrote:
===
-<first line of original message>
-<second line of original message>
.
.
.
-<(n-1)th line of original message>
-<nth line of original message>

  • If the length of the original message is not longer than 512 characters, the worm appends a space.
  • If it is longer than 512 characters, the worm appends three periods (...)

followed by:

<infected computers user's email address>

followed by two lines of Korean text; then:

<infected computers user's email address>

followed by a line of Korean Text.

Attachment: The attachment is one of the following:
  • Opinion.exe
  • Images.exe
  • Card.exe
  • Click.exe
  • Game.exe
  • News_doc.exe
  • Data.exe
  • Click.exe
  • Card.exe
  • Bill.exe
  • Mp3.exe
  • Docs.exe
  • Humor.exe
  • Flash.exe
  • Fun.exe
  • Demo.exe
  • One of 11 file names that contain Korean text.

If the day of the week is Thursday or Monday and the hour of the day is greater than 5, the worm displays this message:



If the current file name is not %windir%\Svchost.exe, or if the argument "Install Me!" was passed to the worm, then the worm displays this dialog box:


  • If you do anything except click Cancel, the worm crashes.
  • If you click Cancel, it displays this message:




Recommendations

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: Douglas Knowles

Discovered: August 02, 2002
Updated: February 13, 2007 11:56:08 AM
Type: Worm
Systems Affected: Windows


NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Update the virus definitions, run a full system scan, and delete all files that are detected as W32.Assarm@mm.
  2. On Windows 95/98/Me, remove the line

    run=%windir%\svchost.exe

    from the Win.ini file.

For details on how to do this, read the following instructions.

To scan for and delete the infected files:
  1. 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.
  2. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
  3. Run a full system scan.
  4. If any files are detected as infected by W32.Assarm@mm, click Delete.

NOTE: (For Windows Me users only) Due to the file-protection process in Windows Me, a backup copy of the file that you are about to edit exists in the C:\Windows\Recent folder. Symantec recommends that you delete this file before you continue with the steps in this section. To do this using Windows Explorer, go to C:\Windows\Recent, and in the right pane select the Win.ini file and delete it. It will be regenerated as a copy of the file that you are about to edit when you save your changes to that file.
  1. Click Start, and click Run.
  2. Type the following, and then click OK.

    edit c:\windows\win.ini

    The MS-DOS Editor opens.

    NOTE: If Windows is installed in a different location, make the appropriate path substitution.
  3. In the [windows] section of the file, look for a line similar to the following:

    run=%windir%\svchost.exe
  4. If the line exists, select the entire line. Ensure that you do not select any other text, and then press Delete.
  5. Click File, and click Save.
  6. Click File, and click Exit.


Writeup By: Douglas Knowles