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  3. Trojan.Zeroaccess.B


Risk Level 1: Very Low

December 22, 2011
November 9, 2012 3:15:51 PM
Infection Length:
Systems Affected:
Windows 2000, Windows 7, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows Server 2008, Windows Vista, Windows XP
Trojan.Zeroaccess.B is a Trojan horse that uses an advanced rootkit to hide itself. It can also create a hidden file system, download more malware, and open a back door on the compromised computer.

Note: The behavior of this threat on 32-bit computers is almost identical to Trojan.Zeroaccess.

For more information, please see the following resource:

Antivirus Protection Dates

  • Initial Rapid Release version December 22, 2011 revision 025
  • Latest Rapid Release version June 24, 2014 revision 006
  • Initial Daily Certified version December 22, 2011 revision 032
  • Latest Daily Certified version July 2, 2013 revision 016
  • Initial Weekly Certified release date December 28, 2011
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Threat Assessment


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


  • Damage Level: Medium
  • Payload: Opens a back door.
    Downloads more malware.


  • Distribution Level: Low
Note: On May 14, 2015, modifications will be made to the threat write-ups to streamline the content. The Threat Assessment section will no longer be published as this section is no longer relevant to today's threat landscape. The Risk Level will continue to be the main threat risk assessment indicator.
Writeup By: Karthik Selvaraj and Rong Zhou

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