Google announced Wednesday that it is acquiring ReCAPTCHA, a company that protects more than 100,000 Web sites from spam and fraud.

ReCAPTCHA, a Carnegie Mellon University spinoff, is a well-known provider of CAPTCHA technology, which is used to prevent spammers from using computers to automatically register for online services, such as webmail accounts and Web site registrations.

Financial terms of the deal were not immediately disclosed Wednesday.

The tool offers simple distorted word puzzles that users fill out to prove they are human, rather than spammers or others automating sign-up.

Google was attracted to ReCAPTCHA since the company has linked its core authentication service with efforts to digitize print books and periodicals. Google currently has a massive effort underway in that area for its Google Books and Google News Archive services.

We'll be applying the technology within Google not only to increase fraud and spam protection for Google products but also to improve our books and newspaper scanning process, reads a post in Google's official blog authored by Luis von Ahn, cofounder of reCAPTCHA, and Will Cathcart, a Google product manager.

Google