Introduced in IE9, SmartScreen automatically checks for potentially malicious software in files you download.
One of the criteria used is the frequency of downloads for this file.
Any "new file", or "new url" is automatically classified as potentially dangerous, and a warning prompt will be displayed to the user.
This warning should quickly disappear after a sufficient number of users download the file.
Microsoft doesn't release any specifics of these numbers. But from our experience, it could go from a few hours to a few days depending on your user base.
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