Feeds

It's ba-ack. Exploit revives slain browser history bug

Attack reveals recently visited websites

SANS - Survey on application security programs

A Google researcher has resurrected an attack that allows website operators to steal the browsing history of visitors almost a year after all major browser makers introduced changes to close the gaping privacy hole.

Proof-of-concept code recently posted by Google security researcher Michal Zalewski works against the majority of people using the Internet Explorer, Chrome, and Firefox browsers. In an informal test carried out by The Register, the attack was able to list recently visited sites on computers running both Microsoft Windows and Apple OS X. It worked even though all three browser makers have patched their wares to stop them from divulging the addresses of sites visited over the past month or so.

“My proof of concept is fairly crude, and will fail for a minority of readers,” Zalewski wrote. “But in my testing, it offers reliable, high-performance, non-destructive cache inspection that blurs the boundary between :visited and all the 'less interesting' techniques.”

Previous exploits usually exploited a mechanism built into all browsers that causes recently visited websites to appear differently than non-visited sites. Attacks based on the CSS, or cascading style sheet, definitions weren't merely theoretical. Last year, academic researchers caught YouPorn.com and 45 other sites pilfering visitors' surfing habits by targeting the browser vulnerability, which first came to light more than a decade earlier

Zalewski said browser makers closed the hole by “severely crippling” CSS functions built around the :visited selectors. His proof-of-concept, according to comments accompanying the sourcecode (link may not work in all browsers), takes a different approach known as cache timing. It starts by loading an iframe tag containing a list of website into the page accessed by the visitor. It then calculates how quickly the websites are rendered. Those that load more quickly must be stored on the browser cache, an indication they have been visited recently.

Cache timing has long been identified as a way to extract browsing history, as noted in a well-known paper (PDF) penned by Princeton University computer scientist Ed Felten. Up to now, the problem with the approach has been that the attacks were slow and easy to detect, making them impractical.

Zalewski said his method was able to overcome these disadvantages by allowing browsers to abort the underlying request quickly. As a result, it's able to test about 50 websites per second with no visible signs that anything is amiss. With minor tweaks – including optimizations, parallelism, and possibly a delay calibration, the code could be capable of detecting “several hundred” URLs. ®

Combat fraud and increase customer satisfaction

More from The Register

next story
Parent gabfest Mumsnet hit by SSL bug: My heart bleeds, grins hacker
Natter-board tells middle-class Britain to purée its passwords
Obama allows NSA to exploit 0-days: report
If the spooks say they need it, they get it
Web data BLEEDOUT: Users to feel the pain as Heartbleed bug revealed
Vendors and ISPs have work to do updating firmware - if it's possible to fix this
Samsung Galaxy S5 fingerprint scanner hacked in just 4 DAYS
Sammy's newbie cooked slower than iPhone, also costs more to build
Mounties always get their man: Heartbleed 'hacker', 19, CUFFED
Canadian teen accused of raiding tax computers using OpenSSL bug
Snowden-inspired crypto-email service Lavaboom launches
German service pays tribute to Lavabit
One year on: diplomatic fail as Chinese APT gangs get back to work
Mandiant says past 12 months shows Beijing won't call off its hackers
prev story

Whitepapers

Designing a defence for mobile apps
In this whitepaper learn the various considerations for defending mobile applications; from the mobile application architecture itself to the myriad testing technologies needed to properly assess mobile applications risk.
3 Big data security analytics techniques
Applying these Big Data security analytics techniques can help you make your business safer by detecting attacks early, before significant damage is done.
Five 3D headsets to be won!
We were so impressed by the Durovis Dive headset we’ve asked the company to give some away to Reg readers.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Securing web applications made simple and scalable
In this whitepaper learn how automated security testing can provide a simple and scalable way to protect your web applications.