A $1 billion copyright infringement lawsuit challenging YouTube’s ability to keep copyrighted material off its popular video-sharing site threatens how hundreds of millions of people exchange all kinds of information on the Internet, YouTube owner Google said.

Google’s lawyers made the claim in papers filed in U.S. District Court in Manhattan as the company responded to Viacom Inc.’s latest lawsuit alleging that the Internet has led to “an explosion of copyright infringement” by YouTube and others.