Viacom Inc. wants YouTube's logs to help determine if unauthorized material makes up a major share of what gets watched there. The media giant, which owns the rights to such shows as “The Colbert Report” and “South Park”, is suing YouTube and corporate parent Google Inc. for copyright infringement.

Viacom General Counsel Michael Fricklas pledged “unequivocally” on Thursday not to use the data to learn the real names of YouTube users in order to sue them for uploading unauthorised clips, as the recording industry has done to people who illegally shared music online.

The company said a protective order dictated that only its outside lawyers and experts could access the raw data, and that it could be used solely to make the case against Google.

But the ruling, filed late Wednesday by Judge Louis Stanton of US District Court in New York, shocked privacy advocates. They fear a broader effect from Stanton’s finding that so-called Internet Protocol addresses — the unique numbers assigned to each computer or device connected to the Internet— need not be strictly protected because they aren't tied publicly to individual names.

Viacom and YouTube are discussing a plan to replace the Internet addresses with codes, a move designed to prevent linking a YouTube log-on name with a particular computer. If that happens, Google has no plans to appeal, according to people working on the case who demanded.

Google had objected to Viacom’s request for the data, arguing that it would violate users’ privacy. But the Mountain View, drew fire from privacy groups because it has written elsewhere, when defending its long-term collection of data on users’ web surfing habits, that Internet addresses aren’t “personally identifiable information.”