SecurityLabs has written an analysis on how spammers increasingly evade Captcha to impersonate humans with bots.

CAPTCHA, or "the Completely Automated Public Turing test to tell Computers and Humans Apart," is a common line of defense against comment spam and false registrations on websites.

Last year CAPTCHA released a means to correct digitized books while checking for spam bots. Dubbed ReCAPTCHA, the project scans book text and enables users to type out the letters they see in the image. According to Wired, ReCAPTCHA is not widely implemented and likely hasn't been cracked by mainstream spammers. Yet.

Not to say ReCAPTCHA is a long-term foil for determined hackers either. Most practical solutions will only slow spammers down, not stop them entirely.

But truly effective anti-bot efforts may simply not be practical for everyday users. "Would you rather be deluged with spam, or have to take a lengthy IQ test every time you post a comment on a blog?" Wired asks.