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Discovered: October 29, 1998
Updated: February 13, 2007 11:34:33 AM
Also Known As: MDEF 9806, MDEF 666, Graphics Accelerator, SevenDust
Type: Virus
Systems Affected: Mac

There are 6 variants of this virus, including 4 polymorphic, encrypted ones. The differences are described below. What they have in common is that they all infect applications by modifying MDEF and MENU resources, and they can create a System Extension (with an invisible character at the beginning of the name so it loads early) or add an INIT resource to the System file. The existence of the extension is the easiest way of identifying its presence without using NAV.

Antivirus Protection Dates

  • Initial Rapid Release version December 21, 2000
  • Latest Rapid Release version May 31, 2016 revision 036
  • Initial Daily Certified version December 21, 2000
  • Latest Daily Certified version June 01, 2016 revision 005

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

Technical Description

SevenDust A: this variant spreads only, it does not cause any damage. Extension name: "666". Size: 850 bytes.

SevenDust B: this variant has a payload which activates every six months and deletes all non-application files. Extension name: "666". Size: 1342 bytes.

SevenDust C: this one is polymorphic and encrypted, no payload. Extension name: "666". Size: 1576 bytes.

SevenDust D: polymorphic, encrypted and symbiotic, no payload. The symbiotic portion alters a 'WIND' resource from the host application and stores its contents within the viral code. Extension name: "666". Size: 2036 bytes.

SevenDust E: polymorphic, encrypted and symbiotic with payload. If launched between 6 and 7 AM on the 6th or 12th of the month it will delete non-application files on the default volume. The symbiotic portion alters a 'MENU' resource from the host application and stores its contents within the viral code. Extension name: "Graphics Accelerator". Size: 2352 bytes plus the size of the symbiotic 'MENU' resource.

SevenDust F: polymorphic, encrypted and symbiotic with payload. If launched between 6 and 7 PM on the 6th of the month it will delete non-application files on the default volume. A Trojan Horse application (named "ExtensionConflict") can initiate one of five sub-strains which infect applications, Control Panels, and/or the System file. Each sub-strain uses a 'MENU' or 'WIND' resource for symbiosis. Some sub-strains will also create an infected System Extension with one of the following names:

  • Graphics Accelerator
  • CD-ROM Driver
  • VideoSync
  • Monitors Plug-In
  • Open Transport
  • PPP.Lib
  • ADSP Tool
  • Photo Access
  • Video Picker
  • ISO 9661 File Access
  • Serial Port
  • XMODEM.Lib
  • TCP/IP.Lib
  • Text Encodings
  • Power Enabler
  • Internet Library
  • AppleTalk Library
  • MacLinkPlus
  • Internet Config
  • Ethernet Ports
These can be distinguished from legitimate versions by the invisible character at the start of the name or by the file creator, which is 'ACCE'. The size of the infection varies from 2844 to 3836 bytes plus the size of the symbiotic resource.

SevenDust G: this strain is similar to SevenDust E with some minor differences. It is polymorphic, encrypted and symbiotic. It will attempt to delete non-application files when executed on the 6th of the month between 6 and 7 PM. It can infect applications by modifying a 'MENU' resource to use its infected 'MDEF'. It uses a 'WIND' resource for symbiosis. It can also create an infected "Graphics Accelerator" extension or alternatively add an infected 'INIT' to the System file.


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.