1. /
  2. Security Response/
  3. W32.Downadup.C


Risk Level 2: Low

March 6, 2009
April 6, 2009 6:30:44 PM
Also Known As:
Mal/Conficker-B [Sophos], Worm:W32/Downadup.DY [F-Secure], Trojan-Downloader.Win32.Kido.a [Kaspersky]
Trojan, Worm
Infection Length:
88,576 bytes
Systems Affected:
Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows Vista, Windows XP
W32.Downadup.C is a threat that is downloaded on to the compromised computer by the W32.Downadup family of worms.

Note: For more information, please see the following resource:

Antivirus Protection Dates

  • Initial Rapid Release version March 6, 2009 revision 036
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version March 6, 2009 revision 037
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date March 11, 2009
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Threat Assessment


  • Wild Level: Medium
  • Number of Infections: 1000+
  • Number of Sites: 10+
  • Geographical Distribution: High
  • Threat Containment: Moderate
  • Removal: Difficult


  • Damage Level: High
  • Payload Trigger: File downloading is triggered after 1st April 2009.
  • Payload: Attempts to download files from a predetermined list of addresses. Also attempts to intercept and redirect DNS requests to prevent access to certain Web sites.
  • Compromises Security Settings: Stops certain Windows services and security related processes.


  • Distribution Level: Medium
  • Target of Infection: Computers already infected by earlier variants of the W32.Downadup family of worms.
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: Ka Chun Leung and Sean Kiernan

Search Threats

Search by name
Example: W32.Beagle.AG@mm
STAR Antimalware Protection Technologies
Internet Security Threat Report