Feeds

Spammers crack Gmail Captcha

Fresh fruit for rotting vegetables

The Power of One eBook: Top reasons to choose HP BladeSystem

Spammers, fresh from the success of cracking the Windows Live captcha used by Hotmail, have broken the equivalent system at Gmail.

Internet security firm Websense reports that miscreants have created bots which are capable of signing up and creating random Gmail accounts for spamming purposes, defeating Captcha-based defences in the process. It reckons the same group of spammers are behind both attacks.

Captcha (Completely Automated Public Turing test to tell Computers and Humans Apart) challenge-response systems, which are used to prevent accounts being created until a user correctly identifies letters in an image, are designed to ensure requests are made by a human rather than an automated program. The technique has been used to defeat automatic sign-ups to email accounts by services including Yahoo! Mail and Gmail for years, and hackers are increasingly successful in defeating the approach. For example, the HotLan Trojan has created more than 500,000 spam email accounts with Hotmail, Yahoo! and Gmail since its arrival back in July 2007.

Websense reckons the latest Gmail Captcha hack is the most sophisticated it has seen to date. Unlike Live Mail Captcha breaking, which involved just one zombie host doing the entire job, the Gmail breaking process involves two compromised hosts. Each of the two compromised hosts applies a slightly different technique to analysing Captcha, as explained in a posting by Websense.

Even using the two techniques, only one in every five Captcha-breaking requests are successful. It's a fairly low percentage, but one that's still more than workable in the case of automated attacks.

It sounds like a lot of effort, but gaining a working Gmail account has a number of advantages for spammers. As well as gaining access to Google's services in general, spammers gain a address whose domain is highly unlikely to be blacklisted, helping them defeat one aspect of anti-spam defences. Gmail also has the benefit of being free to use.

A wide range of Captcha-breaking services are hosted on a domain located in the US, Websense reports. The page includes a support page and payment advice along with an internal test page. ®

The Power of One eBook: Top reasons to choose HP BladeSystem

More from The Register

next story
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
Mozilla fixes CRITICAL security holes in Firefox, urges v31 upgrade
Misc memory hazards 'could be exploited' - and guess what, one's a Javascript vuln
BMW's ConnectedDrive falls over, bosses blame upgrade snafu
Traffic flows up 20% as motorway middle lanes miraculously unclog
LibreSSL RNG bug fix: What's all the forking fuss about, ask devs
Blow to bit-spitter 'tis but a flesh wound, claim team
Manic malware Mayhem spreads through Linux, FreeBSD web servers
And how Google could cripple infection rate in a second
Yorkshire cops fail to grasp principle behind BT Fon Wi-Fi network
'Prevent people that are passing by to hook up to your network', pleads plod
Don't look, Snowden: Security biz chases Tails with zero-day flaws alert
Exodus vows not to sell secrets of whistleblower's favorite OS
Researcher sat on critical IE bugs for THREE YEARS
VUPEN waited for Pwn2Own cash while IE's sandbox leaked
prev story

Whitepapers

Top three mobile application threats
Prevent sensitive data leakage over insecure channels or stolen mobile devices.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Top 8 considerations to enable and simplify mobility
In this whitepaper learn how to successfully add mobile capabilities simply and cost effectively.
Application security programs and practises
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
The Essential Guide to IT Transformation
ServiceNow discusses three IT transformations that can help CIO's automate IT services to transform IT and the enterprise.