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Microsoft Launches JIT-Free 'Super Duper Secure Mode' Edge Browser Experiment

Security engineers at Microsoft plan to rip out a key performance feature from the Edge browser in an experiment to better measure the tradeoffs between security, optimization and performance.

The plan is to create a provocatively named “Super Duper Secure Mode” in Edge that deliberately disables support for the browser’s JavaScript JIT (Just-in-Time) compiler while adding a major anti-exploitation roadblock from Intel Corp.

The new SDSM test -- available in Edge preview builds for select users -- essentially rips out JIT, a feature that makes browsers run faster but data shows that these components introduce attack surfaces that have already been exploited in malware campaigns.

According to Microsoft’s Johnathan Norman, browser makers have traditionally been willing to absorb the security cost to ship “fast” browsers but by disabling JIT from Edge, there is a significant attack surface reduction that could significantly improve user security.

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"[Removing JIT] would remove roughly half of the V8 bugs that must be fixed. For users, this means less frequent security updates and fewer emergency patches required. These updates and patches are common points of frustration for our customers, particularly those in large enterprise environments who must test updates before rolling them out," Norman said in a note explaining the experiment.

In addition to removing JIT, Norman said the browser would be fitted with Intel Corp’s new CET (Control Flow Enforcement Technology), a hardware-based security feature that helps to block certain types of software exploitation.

“Our hope is to build something that changes the modern exploit landscape and significantly raises the cost of exploitation for attackers. Mitigations have a long history of being bypassed, so we are seeking feedback from the community to build something of lasting value,” Norman said.

At a higher level, Norman and his Microsoft Vulnerability Research Team are hoping to trigger a discussion around reconsidering the tradeoffs between security and speed while still delivering a practical browsing experience. 

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“Performance and complexity often come at a cost, and often we bear this cost in the form of security bugs and subsequent patches,” Norman said, pointing to data that shows JIT-related vulnerabilities are constantly being weaponized and used in browser attacks.

During internal lab testing, Norman said a JIT-free version of Edge provided a browsing experience with no noticeable impact on power or memory usage, startup or page-load speeds.

“Anecdotally, we find that users with JIT disabled rarely notice a difference in their daily browsing,” Norman said, even arguing that the JIT-free browser “does not always have negative impacts.”

Microsoft hopes to use the results from the experiment to answer the question of whether the performance gains provided by JIT are worth the resulting security bugs, updates and the missing security mitigations.

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Ryan Naraine is Editor-at-Large at SecurityWeek and host of the popular Security Conversations podcast series. Ryan is a journalist and cybersecurity strategist with more than 20 years experience covering IT security and technology trends. He is a regular speaker at cybersecurity conferences around the world. Ryan has built security engagement programs at major global brands, including Intel Corp., Bishop Fox and Kaspersky GReAT. He is a co-founder of Threatpost and the global SAS conference series. Ryan's career as a journalist includes bylines at major technology publications including Ziff Davis eWEEK, CBS Interactive's ZDNet, PCMag and PC World. Follow Ryan on Twitter @ryanaraine.