Viacom is getting its hands on some of YouTube's sensitive user data as a result of the copyright-infringement lawsuit the conglomerate filed a year ago.

The two companies are in the discovery part of the case and must make certain information available to each other. On Wednesday, a US federal judge ruled that Google must turn over YouTube user activity: videos watched, IP addresses and usernames.

In a statement on Thursday, Google responded to the court's order.

"We are pleased the court put some limits on discovery," Google said in the statement, "including refusing to allow Viacom to access users' private videos and our search technology. We are disappointed the court granted Viacom's over-reaching demand for viewing history. We are asking Viacom to respect users' privacy and allow us to anonymise the logs before producing them under the court's order."

ZDNet.com.au's sister site CNET News.com reported that Viacom is under strict instructions from the court not to use the data for anything other than proving the prevalence of infringement on YouTube.

Viacom, therefore, is forbidden from targeting individual users in the manner of the Recording Industry Association of America's lawsuits against individuals found to be downloading music illegally.

The case is important to internet users because it could help define the scope of the 'safe harbour' provision of the Digital Millennium Copyright Act. That is the part of copyright law that Google and other internet service providers claim protects them from being held responsible for the actions of their users.

The discovery part of the case is not expected to end until some point next year.