Google is stepping up its attack on piracy by using the biggest tool in its arsenal: Search.

The company said that copyright requests will now play a part in its search algorithm, punishing Web sites that receive repeated copyright violation complaints from its users.

In a company blog post, Google said that it will begin taking valid copyright removal notices into account in its ranking algorithm, in order to direct users to “legitimate quality sources of content more easily.”

Over the last 30 days, the company said, it has received copyright removal notices for more than 4.3 million URLs — a figure that outstrips all of the notices the company received in all of 2009.

Search engines have a particularly difficult role to play in the battle against piracy, as they index but have no part in hosting pirated content on sites across the Web. Those advocating for stronger action against copyright violators have said in the past that Google and others weren’t doing enough to keep pirate sites out of search results.

But it’s been difficult for search engines to tackle the problem due simply to the sheer amount of information it would take for a search engine to process what is and isn’t legitimate content.

This move from Google, at least, seems to take a bite out of that problem.

Still, it drew swift concern from the digital rights group Public Knowledge. In a statement, senior staff attorney John Bergmayer said that the system could be abused by those who want to sink competitors’ sites and may harm sites that host a lot of content.

“Google needs to make sure this change does not harm Internet users or the Internet ecosystem,” Bergmayer said.

In a statement of its own, the Motion Picture Association of America hailed the decision and said it was “optimistic that Google’s actions will help steer consumers to the myriad of legal ways for them to access movies and TV shows online.”

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