Feeds

Man knows when you're signed in to GMail, Twitter, Digg

Porn and warez logins ahoy!

SANS - Survey on application security programs

A UK-based web developer has figured out a simple way to tell if visitors to his site are logged in to Gmail, Facebook, Twitter, Digg and thousands of other websites.

One method developed by Mike Cardwell of Nottingham makes use of status codes returned by many sites, which differ depending on whether a user is logged in or not. By embedding a small piece of JavaScript that contains a link to one of the sites he's curious about, he can immediately tell if a visitor is logged in. The method works reliably for Twitter, Facebook and Digg when visitors are browsing with Firefox, Safari or Chrome.

It doesn't work when visitors are using Internet Explorer or Opera.

The exploit works by identifying the HTTP status code that's returned when the visitor's browser encounters the link in Cardwell's script. A 200 code, indicating the request was successfully fulfilled, indicates the person isn't logged in, while 404, 500 and other error codes indicate the opposite.

“This can be an awkward problem to avoid if you're developing a website,” Cardwell writes here. “Some of these requests could be stopped by doing referrer checks; reject all external referrers for content only accessible when logged in.

Detecting whether a visitor is logged in to Gmail requires a different script that generates a hidden image stored in Cardwell's mail folder that's configured to be viewable to everyone. Cardwell said he reported his finding to Google and was told it was “expected behaviour.”

“You may not care that I can tell you're logged into GMail, but would you care if I could tell you're logged into one or more porn or warez sites?” Cardwell asks rhetorically. “Perhaps http://oppressive-regime.example.org/ would like to collect a list of their users who are logged into http://controversial-website.example.com/?” ®

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.