Attributor is showing online publishers how to use plagiarism of their content by other sites to their advantage.

It offers a service that lets publishers track how their articles, images and videos are being used on other sites without permission. Then, it offers ways for these publishers to contact the offending parties and request links back to their content (which, in turn, causes their pages to appear higher in search results, leading to more traffic). Or, it helps them contact the perpetrator and ask for a share of the ad revenue gained from the plagiarized content. Or, send a take-down request.

The Redwood City, Calif. company has been in a roll. It was in private beta with two of the largest publishers in the world, Reuters and the Associated Press, until the end of last year. It has since come out of private beta, and signed up some more big-name clients, including Conde Nast, The Canadian Press, Associated Content, and others.

Its ability to crawl the web and detect content has also allowed it to serve as a sort of web analytics firm. It recently helped provide the Wall Street Journal with an analysis of the size of ad networks like DoubleClick and Google (by far the two market leaders, it found).

Today, it is announcing that it has raised a Series C financing of $12 million led by JAFCO Ventures and current investor Sigma Partners, with participation from existing investors Selby Venture Partners, Draper Richards, First Round Capital and Amicus Capital. It previously raised $10 million.

It plans to use the funds to expand its sales effort and its infrastructure. The company is also committed to extending its services to smaller publishers, co-founder and chief executive Jim Brock tells me, and it already has a number of them using its services.