Tor Browser Counterpunches With a Security Upgrade

June 21, 2016 @ 10:41 AM
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2 min read

Tor is fighting back. The Onion Router (Tor) released version 6.5a1 of its browser in early June, and users will be happy to note that the updated browser contained some welcome security initiatives.

Hardening the Tor Browser

As the Tor Project announced on its blog, the latest version of its browser “updates Firefox to 45.2.0esr and contains all the improvements that went into Tor Browser 6.0.” Specifically, this new release boasts significant security advancements designed to avoid privacy invasions and deanonymization — things Tor is supposed to fundamentally prevent.

The Project worked on the Firefox browser that runs underneath Tor to reduce its potential as an attack surface. This hardening was needed given recent and apparently successful deanonymization attacks, which revealed the identities of Tor users.

A New Way to Randomize Memory

But there’s more: Softpedia reported that this hardened version of the Tor browser includes a new feature called Selfrando. The article described this feature as “an enhanced and practical load-time randomization technique.” This should prevent user identities from ever going public as the result of a cyberattack.

The Tor Project and researchers from the University of California, Irvine have been collaborating to create Selfrando. It is an alternative to the use of address space layout randomization (ASLR), which Tor had used previously. ASLR works by taking code and shifting the memory location in which it runs. Selfrando increases the granularity of code execution by taking each code function separately and then randomizing the memory address.

This can have a major impact on Tor security. If an attacker cannot predict the memory position in which parts of the code will be executing, then use of some sort of memory corruption bug — which could allow them to run malware inside the Tor browser — won’t do them any good.

It remains to be seen whether these hardening efforts will pay off in the future for Tor, but they look encouraging.

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Larry Loeb
Principal, PBC Enterprises

Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE mag...
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