Feeds

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

Porn and warez logins ahoy!

Intelligent flash storage arrays

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/?” ®

Choosing a cloud hosting partner with confidence

More from The Register

next story
Knock Knock tool makes a joke of Mac AV
Yes, we know Macs 'don't get viruses', but when they do this code'll spot 'em
Feds seek potential 'second Snowden' gov doc leaker – report
Hang on, Ed wasn't here when we compiled THIS document
Why weasel words might not work for Whisper
CEO suspends editor but privacy questions remain
DEATH by PowerPoint: Microsoft warns of 0-day attack hidden in slides
Might put out patch in update, might chuck it out sooner
BlackEnergy crimeware coursing through US control systems
US CERT says three flavours of control kit are under attack
China is ALREADY spying on Apple iCloud users, claims watchdog
Attack harvests users' info at iPhone 6 launch
prev story

Whitepapers

Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Top 5 reasons to deploy VMware with Tegile
Data demand and the rise of virtualization is challenging IT teams to deliver storage performance, scalability and capacity that can keep up, while maximizing efficiency.
Mitigating web security risk with SSL certificates
Web-based systems are essential tools for running business processes and delivering services to customers.