CAPTCHA, HACKEDCHA, GOTCHA
By Davey Winder in Editorial
Posted in Uncategorized on
The Completely Automated Public Turing test to tell Computers and Humans Apart security system, thankfully better known by the pseudo-acronym of CAPTCHA, has been well and truly cracked according to reports online. The system uses a set of alpha-numeric characters presented against a background which when combined make it all but impossible for a machine to decipher but easy enough for the human brain to be able to deal with. Or at least that was up until now if these reports are to be believed.
A Russian security ‘researcher’ going by the pseudonym of John Wane has claimed success in bypassing one of the toughest of CAPTCHA implementations, the one to be found at Yahoo! Wane has posted decoder system code online which is said to be accurate to around 35 percent. Now that might not sound significant, but when you are trying to keep the spammer bots at bay I can assure you that it is. As Wane himself says “It’s not necessary to achieve a high degree of accuracy when designing automated recognition software” especially when a spammer can easily hit a rate in excess of 100,000 attempts per day. If they were to manage anything like 30,000 successful account creations then the spam problem, for blogs, forums and the general email population, would rocket overnight.
Application vulnerability software specialists Fortify has warned us all to be vigilant, especially as far as message received from webmail systems are concerned in the light of this possible breach. Fortify Chief Scientist Brian Chess has gone on record to say that “any free email service that is using the CAPTCHA system - or a similar approach to prevent automated sign-ups - is engaged in a never-ending arms race with its attackers.”
It isn’t all bad news though, as CAPTCHA represents just the main gate as it were in the fight against spammers, and the likes of Yahoo! and Google have plenty of other tricks up their collective spam fighting sleeves to prevent an all out flood of malicious mail.
Rated: 100% (1 votes)
Loading ...Comment by Simon Bisson & Mary Branscombe - January 26, 2008 on 4:21 am
I like the kitten captcha-equivalent that Microsoft came up with; not only is image analysis software harder to write than letter scrapers, but every use donates to animal shelters. In the long run, we have to have a robust identity and reputation system - and maybe an exam to prove you’re not stupid enough to buy from spammers before you get to use a service…
Comment by Davey Winder - January 27, 2008 on 2:08 pm
Yep, I was rather enamoured by the MS kittens thing myself. But as you say, ultimately we do have to address the problem of end users having a trailer trash mentality when it comes to spam and link clicking.
Comment by Nick Kotarski - April 2, 2008 on 5:58 pm
Captcha isn’t accessible and the MS kittens thing can only be worse. I find Akismet works pretty well for stopping comment spam. There must be a similar way that would limit the number of signups from a particular IP address.
And yes I know that just about everything can be forged and dynamic IP addresses complicate things.
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