How to troubleshoot definition update issues for Windows Defender beta 2 (918355)

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When you try to run Windows Defender beta 2 or later versions, you may receive the following warning message:To update definitions for Windows Defender beta 2, follow these steps.

Note Each step is unique and may resolve the issue. If the step that you have used does not resolve the issue, go to the next step.

1. Verify that you have the required Microsoft Windows Update prerequisite files. To do this, follow these steps:
   1. Open Microsoft Internet Explorer, and then visit the following Microsoft Web site:

      http://www.windowsupdate.com

   2. Install all prerequisite updates that are available. If you receive an error message, go to step 3.
   3. Click Check for Updates on the Windows Defender beta 2 home page.
2. Uninstall the Windows Defender beta 2 definition file, and then replace it with the most current version of the file. To do this, follow these steps:
   1. Follow the steps in the "Resolution" section of Microsoft Knowledge Base article 915105 to uninstall the current definition file.
      

      915105 Error message after you reinstall Windows Defender Beta 2: "Windows Defender definitions haven't been updated"

   2. Click Check for Updates on the Windows Defender beta 2 home page, or visit the following link to download the current Windows Update Definition Updates:

      http://www.windowsupdate.com

3. The problem may occur because of a Windows Update issue. To troubleshoot a potential Windows Update problem, follow these steps:
   1. Visit the following Microsoft Web site:

      http://v5.windowsupdate.microsoft.com/windowsupdate/v6/troubleshoot.aspx

   2. On the Options Web page, enter keywords that describe the problem. If you cannot resolve the problem, go to step c.
   3. Visit the following Microsoft Web site for more information about how to resolve this problem:

      http://go.microsoft.com/fwlink/?linkID=25127

   4. After you resolve this problem, click Check for Updates on the Windows Defender beta 2 home page.
4. If you are in a corporate environment, a network administrator may be blocking access to Windows Update. Or, you may have a networking configuration problem that relates to third-party products. Contact the network administrator for more information about how you can update definitions for Windows Defender beta 2.
5. In a corporate environment, a network administrator may have deployed the Microsoft Software Update Services server on the network. For example, the network may be using Software Update Service (SUS) 1.0. Windows Defender beta 2 cannot receive updates from SUS 1.0. Contact the network administrator to determine whether this is the problem. In this case, the network administrator must deploy Windows Server Update Services (WSUS). Definitions for Windows Defender must be offered from the WSUS server.
   
   For more information about WSUS, visit the following Microsoft Web site:

   http://www.microsoft.com/windowsserversystem/updateservices/default.mspx

6. Examine the %systemroot%\Windowsupdate.log file for error messages, and then search related Microsoft Knowledge Base articles for more information about errors in the Windowsupdate.log file. To search Microsoft Knowledge Base articles, visit the following Microsoft Web site:

   http://support.microsoft.com