RPX Corporation, provider of a service that aggregates patents to prevent violations and subsequent litigation costs, has brought in an undisclosed amount of second-round funding from Index Ventures, Charles River Ventures and Kleiner Perkins Caufield & Byers.

Based in San Francisco, the company charges companies fees between $35,000 and $4.9 million a year -- a decent exchange for some companies that pay out millions of dollars annually due to patent infringement. RPX actually buys the rights to patents in order to gather the necessary information. It has acquired more than $90 million-worth of rights, it says.