The Gmail CAPTCHA has been cracked--albeit not easily--raising new concerns about spammers' ability to abuse Google's e-mail services. Websense Security Labs pointed out the security breach late last week, noting that spammers have a lot to gain by being able to use bots to automatically sign up for new accounts.

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But, while the CAPTCHA has worked well in the past, hackers are getting better at programming computers with the ability to read them.

That's why there has been some attention focused on creating stronger, harder-to-break CAPTCHAs.

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http://arstechnica.com/security/news/2008/02/gotcha-captcha-gmail-bot-detector-system-cracked.ars