Feeds

CAPTCHA-busting villains branch out from spam into ID theft

'CAPTCHA in the Rye' report delivers captcha and verse

High performance access to file storage

The cybercrooks attempting to defeat CAPTCHAs are no longer just traditional junk-mailers who want to get around the test to send spam. In a recent study, security researchers have discovered that criminals are also using circumvention techniques in attacks that harvest financial or personal data.

A CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is commonly used to distinguish human users from computer automated applications, thus helping to prevent automated tools from abusing online services, such as webmail accounts. Hackers have developed numerous methods to bypass CAPTCHAs, including computer-assisted tools and crowd-sourcing, creating a cat-and-mouse game between miscreants and CAPTCHA providers such as Google and others.

Junk mailers, for example, are interested in defeating CAPTCHA challenges in order to establish webmail accounts for subsequent spam runs. Last weekend spammers managed to spam the UK's open data website by circumventing its CAPTCHA gateway in a slightly more sophisticated variant of the same play.

How do they do it?

Hackers are using computer-assisted tools based on optical character recognition or machine learning technologies as well as tools which outsource CAPTCHA-breaking to modern day sweatshops, typically located in India. More recently miscreants have begun hoodwinking naive users into being a part of the crowd sourced for CAPTCHA solutions. These crowd-sourcing techniques sometimes pose as CAPTCHA-busting games that reward players. Some CAPTCHA-busting sites offer free porn as an incentive.

Not just about spam anymore

However hackers might also be interested in circumventing CAPTCHAs as a means to collect financial or personal details, according to the new study by data security firm Imperva.

Attacks based on CAPTCHA-busting have now been used to access a system for filing financial status reports maintained by one of the central banks in Argentina. Criminals have also launched attacks designed to obtain tax details associated with a Brazilian social security number. Hackers have also targeted the website of an agency in charge of the voting process in Brazil. All three sets of attacks are likely one important part in a more elaborate set of scams, most likely involving ID theft.

In response, CAPTCHA providers need to step up their game to make life harder for miscreants. Approaches on offer include delivering more difficult CAPTCHAs to potentially suspicious users or integrating simple riddles and contextual semantics to beef up challenges. Approaches such as traffic-based automation detection, behavioural analysis, content analysis and blacklists can help distinguish suspicious parties from genuine surfers.

Improvements to the security of CAPTCHA can be made without making life too difficult for legitimate users, according to Imperva.

"CAPTCHA security, like many other security segments, is a battle of innovation between hackers and security professionals," said Amichai Shulman, CTO of Imperva. "CAPTCHA security must be balanced against a positive user experience, but can readily be improved by deploying anti-automation solutions to help prevent hackers from employing anti-CAPTCHA tools."

The June edition of Imperva's Hacker Intelligence report, A CAPTCHA in the Rye explaining the threat in greater depth, can be found here. ®

High performance access to file storage

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
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
Call of Duty 'fragged using OpenSSL's Heartbleed exploit'
So it begins ... or maybe not, says one analyst
NSA denies it knew about and USED Heartbleed encryption flaw for TWO YEARS
Agency forgets it exists to protect communications, not just spy on them
prev story

Whitepapers

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.
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.
HP ArcSight ESM solution helps Finansbank
Based on their experience using HP ArcSight Enterprise Security Manager for IT security operations, Finansbank moved to HP ArcSight ESM for fraud management.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Mobile application security study
Download this report to see the alarming realities regarding the sheer number of applications vulnerable to attack, as well as the most common and easily addressable vulnerability errors.