Threat Explorer

The Threat Explorer is a comprehensive resource consumers can turn to for daily, accurate, up-to-date information on the latest threats, risks and vulnerabilities.

Downloader.Mimail

Downloader.Mimail

Discovered:
04 August 2003
Updated:
13 February 2007
Systems Affected:
Windows


Downloader.Mimail is a program that downloads W32.Mimail.A@mm from a Web site, and then executes it. This appears to have been spammed to a large number of users. This program has no means of distributing itself to additional users.

Antivirus Protection Dates

  • Initial Rapid Release version 05 August 2003
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 05 August 2003
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date 06 August 2003
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Downloader.Mimail arrives as a .zip file. An HTML file that exploits an Internet Explorer vulnerability exists inside the zip file. More information and the patch related to this vulnerability can be found in the Microsoft Document MS03-014: April, 2003, Cumulative Patch for Outlook Express (article ID 330994) .

When the HTML file is opened:
  • An embedded executable runs and downloads W32.Mimail.A@mm from a Web site.
  • Saves it in the Windows System directory, and then executes it.


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: Fergal Ladley