The following determine whether you are prevented from opening the file or whether you are warned before you open the file:
- The type of program that you are using.
- The file type that you are downloading or trying to open.
- The security settings of the Web content zone that you are downloading the file from.
Note You can configure the Web content zones in Microsoft Internet Explorer on the Security tab. To view the Web content zones, click Tools, click Internet Options, and then click the Security tab. The following are the four Web content zones:
- Local intranet
- Trusted sites
- Restricted sites
The Attachment Manager uses the IAttachmentExecute application programming interface (API) to find the file type, to find the file association, and to determine the most appropriate action.
Microsoft Outlook Express, Microsoft Windows Messenger, Microsoft MSN Messenger, and Microsoft Internet Explorer use the Attachment Manager to handle e-mail attachments and Internet downloads.
The Attachment Manager classifies files that you receive or that you download based on the file type and the file name extension. Attachment Manager classifies files types as high risk, medium risk, and low risk. When you save files to your hard disk from a program that uses the Attachment Manager, the Web content zone information for the file is also saved with the file. For example, if you save a compressed file (.zip) that is attached to an e-mail message to your hard disk, the Web content zone information is also saved when you save the compressed file. When you try to extract the contents from the compressed file, or if you try to run a file, you cannot. The Web content zone information is saved together with the files only if the hard disk uses the NTFS file system.
You can open a blocked file from a known source if you want to. To open a blocked file, follow these steps:
- Right-click the blocked file, and then click Properties.
- In the General tab, click Unblock.
High-risk file types
When you try to download or open a file from a Web site that is in the restricted Web content zone, you may receive a message that indicates that the file is blocked.
When you try to open high-risk file types from sites that belong to the Internet Web content zone, you may receive a warning message, but you may be able to open these types of files.
The file types that the Attachment Manager labels as high-risk include the following:
Medium-risk file types
File types that the Attachment Manager does not label as high risk or low risk are automatically labeled as medium risk.
When you open a medium-risk file from the Internet Web content zone or from the restricted sites Web content zone, you may receive a warning message, but you may be able to open these types of files.
Low-risk file types
The Attachment Manager labels the following file types as low risk only when you open them by using Notepad. If you associate another program with this file type, the file type is no longer considered low risk.
The Attachment Manager labels the following file types as low risk only when you open the file by using the Microsoft Windows Picture and Fax Viewer:
Associating a file type with Notepad or with the Windows Picture and Fax Viewer does not add that file type to the list of low-risk file types.