SmartScreen (officially calledWindows SmartScreen,Windows Defender SmartScreen andSmartScreen Filter in different places) is acloud-basedanti-phishing andanti-malware component included in severalMicrosoft products:
SmartScreen as a business unit includes the intelligence platform, backend, serving frontend, UX, policy, expert graders, andclosed-loop intelligence (machine learning andstatistical techniques) designed to help protect customers from safety threats likesocial engineering anddrive-by downloads.
SmartScreen was first introduced inInternet Explorer 7, then known as thePhishing Filter. Phishing Filter does not check every website visited by the user, only those that are known to be suspicious.[1]
With the release ofInternet Explorer 8, the Phishing Filter was renamed to SmartScreen and extended to include protection from socially engineered malware. Every website and download is checked against a local list of popular legitimate websites; if the site is not listed, the entire address is sent to Microsoft for further checks.[2] If it has been labeled as animpostor or harmful, Internet Explorer 8 will show a screen prompting that the site is reported harmful and shouldn't be visited. From there the user can either visit theirhomepage, visit the previous site, or continue to the unsafe page.[3] If a user attempts to download a file from a location reported harmful, then the download is cancelled. The effectiveness of SmartScreen filtering has been reported to be superior to socially engineered malware protection in other browsers.[4]
According to Microsoft, the SmartScreen technology used by Internet Explorer 8 was successful against phishing or other malicious sites and in blocking ofsocially engineered malware.[5]
Beginning with Internet Explorer 8, SmartScreen can be enforced usingGroup Policy.
InInternet Explorer 9, SmartScreen added protection againstmalware downloads by launching SmartScreen Application Reputation to identify both safe and malicious software. The system blocked known malware while warning the user if an executable was not yet known to be safe. The system took into account the download website’s reputation based on SmartScreen’sphishingfilter launched in priorweb browser versionsInternet Explorer 7 andInternet Explorer 8.[6]
Internet Explorer Mobile 10 was the first release of Internet Explorer Mobile to support the SmartScreen Filter.[7]
Microsoft Edge [Legacy] was Microsoft's new browser beginning inWindows 10, built on the same Windows web platform powering Internet Explorer.Microsoft Edge was later rebuilt onGoogle'sChromium browser stack to go cross-platform ontomacOS and down-level intoWindows 8.1 and below. SmartScreen shipped with each version of Microsoft Edge, mostly with Internet Explorer parity, in progressive versions adding protection improvements targeting new consumer threat classes liketech support scams or adding new enterprise configurability features.
In October 2017, criticisms regarding URL submission methods were addressed with the creation of theReport unsafe site URL submission page. Prior to 2017, Microsoft required a user to visit a potentially dangerous website to use the in-browser reporting tool, potentially exposing users to dangerous web content. In 2017, Microsoft reversed that policy by adding the URL submission page, allowing a user to submit an arbitrary URL without having to visit the website.
SmartScreen Filter inMicrosoft Outlook was previously bypassable due to a data gap in Internet Explorer. Some phishing attacks use a phishing email linking to a front-end URL unknown to Microsoft; clicking this URL in the inbox opens the URL in Internet Explorer; the loaded website then, using client-side or server-side redirections, redirects the user to the malicious site.[8] In the original implementation of SmartScreen, the "Report this website" option in Internet Explorer only reported the currently-open page (the final URL in the redirect chain); the original referrer URL in the phishing attack was not reported to Microsoft and remained accessible. This was mitigated beginning with some versions ofMicrosoft Edge Legacy by sending the full redirection chain to Microsoft for further analysis.
InMicrosoft Windows 8, SmartScreen added built-inoperating system protections againstweb-delivered malware performing reputation checks by default on any file or applicationdownloaded from the Internet, including those downloaded fromemail clients likeMicrosoft Outlook or non-Microsoftweb browsers likeGoogle Chrome.[9][10]
Windows SmartScreen functioned inline at theWindows shell directly prior to execution of any downloaded software.
Whereas SmartScreen inInternet Explorer 9 warned against downloading and executing unsafe programs only in Internet Explorer, Windows SmartScreen blocked execution of unsafe programs of anyInternet origin.
With SmartScreen left at its default settings,administrator privilege would be required to launch and run an unsafe program.
Microsoft faced concerns surrounding the privacy, legality and effectiveness of the new system, suggesting that the automatic analysis of files (which involves sending a cryptographic hash of the file and the user's IP address to a server) could be used to build a database of users' downloads online, and that the use of the outdatedSSL 2.0 protocol for communication could allow an attacker to eavesdrop on the data. In response, Microsoft later issued a statement noting that IP addresses were only being collected as part of the normal operation of the service and would be periodically deleted, that SmartScreen on Windows 8 would only use SSL 3.0 for security reasons, and that information gathered via SmartScreen would not be used for advertising purposes or sold to third parties.[11]
Beginning inWindows 10, Microsoft placed the SmartScreen settings into theWindows Defender Security Center.[12]
Further Windows 10 andWindows 11 updates have added more enterprise configurability as part of Microsoft's enterpriseendpoint protection product.
Outlook.com uses SmartScreen to protect users from unsolicited e-mail messages (spam/junk), fraudulent emails (phishing) and malware spread via e-mail. After its initial review of the body text, the system focuses on the hyperlinks and attachments.
To filter spam, SmartScreen Filter uses machine learning fromMicrosoft Research which learns from known spam threats and user feedback when emails are marked as "Spam" by the user.
Over time, these preferences help SmartScreen Filter to distinguish between the characteristics of unwanted and legitimate e-mail and can also determine the reputation of senders by a number of emails having had this checked. Using these algorithms and the reputation of the sender is an SCL rating (Spam Confidence Level score) assigned to each e-mail message (the lower the score, the more desirable). A score of -1, 0, or 1 is considered not spam, and the message is delivered to the recipient's inbox. A score of 5, 6, 7, 8, or 9 is considered spam and is delivered to the recipient's Junk Folder. Scores of 5 or 6 are considered to be suspected spam, while a score of 9 is considered certainly spam.[13] The SCL score of an email can be found in the various x-headers of the received email.
SmartScreen Filter also analyses email messages from fraudulent and suspicious Web links. If such suspicious characteristics are found in an email, the message is either[clarification needed] directly sent to the Spam folder with a red information bar at the top of the message which warns of the suspect properties. SmartScreen also protects against spoofed domain names (spoofing) in emails to verify whether an email is sent by the domain which it claims to be sent. For this, it uses the technologySender ID andDomainKeys Identified Mail (DKIM). SmartScreen Filter also ensures that one email[clarification needed] from authenticated senders can distinguish more easily by placing a green-shield icon for the subject line of these emails.[14][15]
 | This section needs to beupdated. Please help update this article to reflect recent events or newly available information.(March 2023) |
In late 2010, the results of browser malware testing undertaken by NSS Labs were published.[16] The study looked at the browser's capability to prevent users followingsocially engineered links of a malicious nature and downloading malicious software. It did not test the browser's ability to block malicious web pages or code.
According to NSS Labs, Internet Explorer 9 blocked 99% of malware downloads compared to 90% for Internet Explorer 8 that does not have the SmartScreen Application Reputation feature as opposed to the 13% achieved byFirefox,Chrome, andSafari; which all use aGoogle Safe Browsing malware filter.Opera 11 was found to block just 5% of malware.[17][18][19] SmartScreen Filter was also noted for adding legitimate sites to its blocklists almost instantaneously, as opposed to the several hours it took for blocklists to be updated on other browsers.
In early 2010, similar tests had given Internet Explorer 8 an 85% passing grade, the 5% improvement being attributed to "continued investments in improved data intelligence".[20] By comparison, the same research showed that Chrome 6, Firefox 3.6 and Safari 5 scored 6%, 19% and 11%, respectively. Opera 10 scored 0%, failing to "detect any of the socially engineered malware samples".[21]
In July 2010, Microsoft claimed that SmartScreen on Internet Explorer had blocked over a billion attempts to access sites containing security risks.[22] According to Microsoft, the SmartScreen Filter included in Outlook.com blocks 4.5 billion unwanted e-mails daily from reaching users. Microsoft also claims that only 3% of incoming email is junk mail but a test by Cascade Insights says that just under half of all junk mail still arrives in the inbox of users.[23][24] In a September 2011 blog post, Microsoft stated that 1.5 billion attempted malware attacks and over 150 million attempted phishing attacks have been stopped.[25]
In 2017, Microsoft addressed criticisms about the URL submission process by creating a dedicated page to report unsafe sites, rather than requiring users to visit the potentially dangerous site.[26]
SmartScreen expanded to protect users against new threats such as tech-support scams, potentially unwanted applications (PUAs), and drive-by attacks that do not require user interaction.[27]
Manufacturers of other browsers have criticized the third-party tests which claim Internet Explorer has superior phishing and malware protection compared to that of Chrome, Firefox, or Opera. Criticisms have focused mostly on the lack of transparency of URLs tested and the lack of consideration of layered security additional to the browser, withGoogle commenting that "The report itself clearly states that it does not evaluate browser security related to vulnerabilities in plug-ins or the browsers themselves",[28] and Opera commenting that the results appeared "odd that they received no results from our data providers" and that "social malware protection is not an indicator of overall browser security".[29]
SmartScreen builds reputation based on code signing certificates that identify the author of the software. This means that once a reputation has been built, new versions of an application can be signed with the same certificate and maintain the same reputation.
However, code signing certificates need to be renewed every two years. SmartScreen does not relate a renewed certificate to an expired one. This means that reputations need to be rebuilt every two years, with users getting frightening messages in the meantime.Extended Validation (EV) certificates seem to avoid this issue, but they are expensive and difficult to obtain for small developers.[30]
SmartScreen Filter creates a problem for small software vendors when they distribute an updated version of installation or binary files over the internet.[31] Whenever an updated version is released, SmartScreen responds by stating that the file is not commonly downloaded and can therefore install harmful files on your system. This can be fixed by the author digitally signing the distributed software. Reputation is then based not only on a file's hash but on the signing certificate as well. A common distribution method for authors to bypass SmartScreen warnings is to pack their installation program (for example Setup.exe) into aZIP-archive and distribute it that way, though this can confuse novice users.
Another criticism is that SmartScreen increases the cost of non-commercial and small scale software development. Developers either have to purchase standard code signing certificates or more expensive extended validation certificates. Extended validation certificates allow the developer to immediately establish reputation with SmartScreen[32] but are often unaffordable for people developing software either for free or not for immediate profit. The standard code signing certicates however pose a "catch-22" for developers, since SmartScreen warnings make people reluctant to download software, as a consequence to get downloads requires first passing SmartScreen, passing SmartScreen requires getting reputation and getting reputation is dependent on downloads.