After a user downloads a file, IE9 thinks the entire site is a threat

Before downloading the file, the site checks out fine. After downloading an .exe (non-malicious; an installer for an app used internally by website staff), the browser alerts:

This website has been reported to contain the following threats:

• Malicious software threat: This site contains links to viruses or other software programs that can
• reveal personal information stored or typed on your computer to malicious persons.

Checking on a different computer, the site is fine. After downloading the .exe, the same message appears 开发者_运维百科again.

Why does this happen? More importantly, how do I prevent it from happening?

The same does not happen in Firefox or Chrome or Safari, using their similar malware-checking features.

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Do you have control over the file that is being downloaded? If so, wrap it in compression (zip, rar, or something else). Browsers do not like .exe files being downloaded.

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Make the user physically have a link to the download, in a compressed format would also help. A site that tries to send the user a *.exe file would look suspicious to any browser that cares at all for its user.