How CAPTCHA got trashed

The wiggly words are now most useful for malware authors
Page:

CAPTCHA used to be an easy and useful way for Web administrators to authenticate users. Now it's an easy and useful way for malware authors and spammers to do their dirty work.

CAPTCHA -- Completely Automated Public Turing Test to Tell Computers and Humans Apart -- was a good idea in its day. You presented users with an obfuscated string of characters and then had them decode and type the string in to get an e-mail account, a social networking account or comment access on an online forum. Not much fuss (though users justifiably complained that the difference between 1 (one) and l (the lower-case letter l) can be hard to see in many fonts) and certainly no muss from a Web administrator's point of view.

So it was that CAPTCHA went from relatively obscure security measure perfected in 2000 by researchers at Carnegie Mellon University to deployment by most of the major Web e-mail sites and many other Web sites by 2007. Sites such as Yahoo Mail, Google's Gmail and Microsoft's Hotmail all used -- and, for that matter, continue to use -- CAPTCHA to make sure that only human beings, not bots, could get accounts or make postings.

Those days are long gone.

By January 2008, Yahoo Mail's CAPTCHA had been cracked. Gmail was ripped open in April. Hotmail's top got popped during the same month.

And then things got bad.

There are now programs available online (no, we will not tell you where) that automate CAPTCHA attacks. You don't need to have any cracking skills. All you need is a desire to spread spam, make anonymous online attacks against your enemies, propagate malware or, in general, be an online jerk.

It's not just free e-mail sites that can be made to suffer, though.

John Nagle, founder of SiteTruth, a site that tries to identify bogus businesses and their Web sites, wrote in late May on Techdirt that while spam on the popular online classified ad service Craigslist "has been a minor nuisance for years ... this year, the spammers started winning and are taking over."

Craigslist tried "to stop spamming by checking for duplicate submissions," Nagle explained. "They check for excessive posts from a single IP address. They require users to register with a valid e-mail address. They added a CAPTCHA to stop automated posting tools. And users can flag postings they recognize as spam."

Page:
More about: Carnegie Mellon University, Google, Mellon, MessageLabs, Microsoft, Quantum, Websense, Yahoo
References show all

Comments

1

Darrell Shandrow

Tue 16/06/2009 - 06:04

New Techniques Must Include Accessibility

Any "new techniques" that replace the traditional CAPTCHA must include alternatives that reasonably accommodate the needs of the blind and visually impaired. The proposed 3D solution is definitely not appropriate, as it further complicates the problem. We blind accessibility evangelists want protection against spam just like our sighted peers, but we will not accept ongoing, pervasive discrimination inherent in visual-only security schemes.

2

gnujohn

Tue 16/06/2009 - 18:29

on the captcha variant used by qrbgs: a corrective

Quantum Random Bit Generators don't require calculus for their bot-fighter; but they might ask an easy question about the least zero of an (already factored) polynomial, for example, such as p(x) = (x+4)(x-6)(x+5)(x-4)(x-4) . Such a question doesn't ask for calculus, but asks for some high-school algebra. QRBG also say that they'll provide an easier question on request. Still, it's more than copying a nonsense blurb.

3

autoauctions0267

Fri 01/10/2010 - 01:54

You certainly deserve a round of applause for your post and more specifically, your blog in general. Very high quality material

4

Rapidshare Search

Fri 21/01/2011 - 00:58

I have many question about your post. I think u should write lot of more details. But Thanks anymore

5

who is lookup

Tue 22/02/2011 - 23:50

due recently reinstalled the operating arrangement, and it took a batch of things in identical place

Post new comment

The content of this field is kept private and will not be shown publicly.
Users posting comments agree to the Computerworld comments policy.
Login or register to link comments to your user profile, or you may also post a comment without being logged in.
Related Whitepapers
Latest Stories
Community Comments
Whitepapers
All whitepapers
Sign up now to get free exclusive access to reports, research and invitation only events.
Featured Download
/downloads/product/165/billings/

Billings

Billings allows you to present clients with professional looking invoices. There are 30 templates to choose from and you can add your own logo and ...

Computerworld newsletter

Join the most dedicated community for IT managers, leaders and professionals in Australia