The United States Patent and Trademark Office claims that file-sharing sites could be setting up children for copyright infringement lawsuits and compromising national security.

"A decade ago, the idea that copyright infringement could become a threat to national security would have seemed implausible," Patent and Trademark Director Jon Dudas said in a report released this week. "Now, it's a sad reality."

The report, which the patent office recently forwarded to the U.S. Department of Justice, states that peer-to-peer networks could manipulate sites so children violate copyright laws more frequently than adults. That could make children the target in most copyright lawsuits and, in turn, make those protecting their material appear antagonistic, according to the report.

File-sharing software also could be to blame for government workers who expose sensitive data and jeopardize national security after downloading free music on the job, the report states.

"There are documented incidents of P2P file sharing where Department of Defense sensitive documents have been found on non-U.S. computers with no protection against hostile intelligence," the Patent and Trademark Office explained in a statement.

In 2005, the Department of Homeland Security announced that government workers had installed file-sharing programs that accessed classified information without their knowledge.

"There will almost never be a legitimate business or governmental justification for employee use of file-sharing programs," the report said. "Nevertheless, preventing employees from using these programs on corporate or government networks can be both difficult and expensive."

Some unanswered questions raised in the report could be addressed by consumer-protection advocates or agencies or by computer science researchers, the report states.

Dudas said he commissioned the report after hearing some of the information the authors compiled for a law review article. After publishing the report on his office's Web site last week, he urged further investigation.