IE8 Security Part III: SmartScreen® Filter


Internet Explorer Team Blog

IE8 Security Part III: SmartScreen® Filter

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As someone whose email address is posted in thousands of forum posts, newsgroup discussions, and blogs, I get a lot of spam. Of the spam I receive, a significant number of messages represent phishing attacks. Most of these lures aren’t very clever or convincing, but phishing has become a simple numbers game—hosting phishing sites is cheap, and even if only a few users fall for any given phishing attack, attackers will profit by increasing the volume of phishing campaigns.

In Internet Explorer 7, we introduced the Phishing Filter, a dynamic security feature designed to warn users when they attempt to visit known-phishing sites, and worked with partners to introduce Extended Validation certificates that light up the address bar when users visit sites with verified identity information. Beyond the Phishing Filter, Microsoft has also published educational materials on identifying phishing scams, and developed a strategy to attack phishing at multiple levels.

For Internet Explorer 8, we’ve built upon the success of the Phishing Filter feature (which blocks over a million phishing attacks weekly) to develop the SmartScreen® Filter, a replacement that improves upon the Phishing Filter in a number of important ways:

  • Improved user interface
  • Faster performance
  • New heuristics & enhanced telemetry
  • Anti-Malware support
  • Improved Group Policy support

I’ll describe each of these in the sections that follow.

Improved User Interface
First, we’ve simplified the opt-in experience for the SmartScreen Filter, integrating the option into the IE first-run experience. After first-run, you can later change your preferences easily by using the option on the classic Tools menu.

Next, the bold new SmartScreen blocking page offers clear language and guidance to help you avoid known-unsafe websites. Here’s a screenshot from a recent phishing site I encountered:

SmartScreen Blocking Page

The “Go to my homepage” link enables you easily to navigate away from the unsafe website to start browsing from a trusted location. If you instead choose to ignore the SmartScreen warning by clicking the “Disregard and continue” link, the address bar remains red as a persistent warning as long as you are on the unsafe site.

If you uncover a new phishing site, you can submit it for analysis using the “Report Unsafe Website” option on the Tools menu. In the unlikely event of a false-positive, you can provide feedback using the “Report that this is not an unsafe website” link on the blocking page or by clicking the “Unsafe Website” flyout in the address bar.

Improved Performance
As a part of our overall investment in improving performance across Internet Explorer, we’ve made several performance tweaks to the SmartScreen Filter to improve its speed and lower its impact on browser performance. Detection of unsafe sites happens in parallel with navigation, so you can confidently surf the web without being forced to make a tradeoff between speed and safety.

New heuristics & telemetry
As attackers have evolved their phishing sites in an attempt to avoid being recognized and blocked, the SmartScreen Filter has also evolved to catch more phish than ever before. New heuristics, developed with help from security research teams across Microsoft, are able to evaluate more aspects of web pages to detect suspicious behavior. These new heuristics, combined with enhanced telemetry, allow the URL Reputation Service to identify and block phishing sites faster than ever.

In rare cases, SmartScreen will request feedback on sites of unknown reputation, as shown in this screenshot:

SmartScreen Feedback Request Page

User feedback about unknown sites is collected by the SmartScreen web service and quickly evaluated to block new phish as they are discovered in the wild.

Anti-Malware Support
The SmartScreen Filter goes beyond anti-phishing to help block sites that are known to distribute malware, malicious software that attempts to attack your computer or steal your personal information. There are many types of malware, but most types can impact your privacy and security. The SmartScreen anti-malware feature is URL-reputation-based, which means that it evaluates the servers hosting downloads to determine if those servers are known to distribute unsafe content. SmartScreen’s reputation-based analysis works in concert with other signature-based anti-malware technologies like the Malicious Software Removal Tool, Windows Defender, and Windows Live OneCare, in order to provide comprehensive protection against malicious software.

If you are lured to a site known to distribute malware, the SmartScreen blocking page is displayed and indicates that the server is known to distribute unsafe software:

SmartScreen Blocking Page for Server Known to Distribute Malware

On the other hand, if you click on a direct link to a download (from an instant message, for instance) hosted by a known-malicious site, the Internet Explorer download dialog will interrupt the download to warn you of the threat:

Unsafe Download Warning Dialog

SmartScreen’s anti-malware feature complemented by the IE8 features that combat malicious repurposing or exploit of browser add-ons, helps to protect you from a full range of malicious websites.

Group Policy Support
Group Policy can be used to enable or disable the SmartScreen Filter for Internet Explorer users across an entire Windows domain. A new Group Policy option is available that allows domain administrators to block users from overriding SmartScreen Filter warnings. When Group Policy restrictions are enabled, the option to override the SmartScreen warning screen is removed from the blocking pages and download dialog.

SmartScreen Warning Page with Override Removed

As outlined in Dean’s post last week, Privacy is a core component of trustworthy browsing. As with IE7, Microsoft remains committed to helping ensure users’ privacy while providing protection from unsafe websites. URL data submitted to the SmartScreen web service for evaluation is transmitted in encrypted format over HTTPS. The data is not stored with a user's IP address or other personally identifiable information. Because user privacy is important in all Microsoft's products and technologies, Microsoft has taken steps to help ensure that no personally identifiable information is retained or used for purposes other than improving online safety; data will not be used to identify, contact, or provide advertising to users. You can read more in our privacy statement.

Web criminals are increasingly relying on social engineering attacks to engage in their criminal enterprises, but we’re working hard to deliver the tools to help keep you safe on the web. The IE8 SmartScreen Filter is designed to combat both phishing and malware sites while protecting your privacy and enabling high-performance browsing. I strongly recommend you enable the SmartScreen Filter and give it a spin in IE8 Beta 2, due in August.

Please stay tuned to the IEBlog for further posts on IE8 Security improvements!

Eric Lawrence
Program Manager
Internet Explorer Security

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