Attachment manager in Windows: Configuring high, medium and low risk files

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The Attachment Manager on Windows is a service that is enabled when you receive an email message with an attachment and dangerous files that you can save from the Internet. In this article, we will see how to configure high, medium and low risk files.

Microsoft Outlook Express, Microsoft Windows Messenger and Microsoft Internet Explorer use Attachment Manager to manage Internet attachments and downloads.

Attachment Manager under Windows 10/8/7

The Attachment Manager protects you against dangerous attachments and downloads by identifying the file type and corresponding security settings. If it identifies an attachment that may not be secure, it prevents the file from opening or warns you before you open the file.

It uses the programming interface (API) IAttachmentExecute to find the file type and file association. When one of these applications saves a downloaded file to an NTFS formatted hard disk, it updates the file metadata with the area from which it was downloaded. Metadata is stored as Alternative Data Stream (ADS). If you want to unlock a downloaded file, you can do so by right-clicking, selecting Properties and clicking Unlock.

It checks the following 3 things :

  • The type of program you are using.
  • The type of file you are trying to download or open
  • The security settings of the web content area from which you are downloading the file.

It classifies file types as high, medium and low.

  • High risk – Blocks file opening if file is from restricted area and issues a Windows security warning: Windows has determined that this file is potentially dangerous. To protect your computer, Windows has blocked access to this file.
  • Moderate Risk – Indicated with a warning: The publisher could not be verified. Are you sure you want to use this software?
  • Low risk – Opens file without message.

The attachment manager only designates the following file types as low risk if you open them with Notepad. If you assign another program to this file type, the file type is no longer considered low-risk:.log,.text,.txt. The attachment manager also marks the following file types as low-risk only if you open the file with the Microsoft Windows Image and Fax Viewer :.bmp,.dib,.emf,.gif,.gif,.ico,.jfif,.jpg,.jpe,.jpeg,.jpeg,.png,.tif,.tiff,.wmf.

If you try to download or open a file from a website that is within the restricted web content area, you may receive a message that the file is blocked. If you attempt to open high-risk file types from websites within the Internet content area, you may receive a warning message, but you can open the selected file types.

File types that are not marked as risky or low risk by the attachment manager are automatically marked as medium risk.

Disable the Attachment Manager unlock function. Automatically unlock downloaded files.

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YOU DO NOT WANT TO DO IT, but if you want to disable this Attachment Manager feature, you can do so via Group Policy > User Configuration > Administration Templates > Windows Components > Attachment Manager.

Double-click Do not store zone information in attachments to open the settings window and enable the setting here. If you enable this policy setting, Windows does not mark attachments with their zone information.

This policy setting allows you to manage whether Windows marks attachments with information about their area of origin (restricted, Internet, Intranet, local). This requires NTFS to work properly and will fail without notice on FAT32. Because the area information is not preserved, Windows cannot perform an appropriate risk assessment.

If you enable this policy setting, Windows does not highlight attachments with their zone information. If you disable this policy setting, Windows marks attachments with their zone information. If you do not configure this policy setting, Windows marks attachments with their zone information.

You can also open Registry Editor and navigate to the next registry key instead;


Change the value of SaveZoneInformation from 2 by default to 1.

You can see various other policy settings for Attachment Manager. For more information about configuring the attachment manager, see KB883260


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