Microsoft Boosts Security in IE9
In a statement describing the features of IE9, Microsoft says that SmartScreen Filter:
uses reputation data to remove unnecessary warnings for well-known files, and show more severe warnings when the download has a higher risk of being malicious ... Other browsers show the same warning whether a file is an extremely common program or a piece of malware created literally minutes ago. Internet Explorer 9 is the only browser that uses download reputation to help users make safety decisions.
Microsoft goes on to say:
Download Manager makes several security-related checks on downloads: scans for viruses, verifies that an executable file comes from a trusted source and uses reputation data to inform you of potentially dangerous downloads.
The security capabilities are not available in the initial release of Internet Explorer 9 Beta, but will be activated soon after the Beta release. Users will not need to upgrade to get the capabilities.