NEW YORK—A $1 billion copyright infringement lawsuit over 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, owner Google Inc. said.

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

The back-and-forth between the companies has intensified since Viacom brought its lawsuit last year, saying it was owed damages for the unauthorized viewing of its programming from MTV, Comedy Central and other networks, including such hits as “The Daily Show with Jon Stewart.”

In papers submitted to a judge late Friday, Google said YouTube “goes far beyond its legal obligations in assisting content owners to protect their works.”

It said that by seeking to make carriers and hosting providers liable for Internet communications, Viacom “threatens the way hundreds of millions of people legitimately exchange information, news, entertainment and political and artistic expression.”