Google, Worms and CAPTCHAs

At the recently held WORM 2006 workshop, Niels Provos (Google) in his presentation, informed us that CAPTCHAs were used by Google in preventing worm attacks.

Some worms (I don't recollect the details and don't have my notes handy now) use Google to search for email addresses to mail themselves to. Google used CAPTCHAs to prevent such automated web attacks.

Will update this post with more details soon.

UPDATE 4/29/2007:
Found the details. It was the Slaty Worm against which CAPTCHAs were used by the Google team. The research paper detailing this is titled "Search Worms".

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