This much is known: In its hunt for information about three people it believes to be associated with the whistle-blower site WikiLeaks, the Justice Department has sought to extract details about them and their communications on Twitter. What is not yet known is where else the Justice Department went looking.

On Friday, lawyers for the American Civil Liberties Union and the Electronic Frontier Foundation asked a federal court in Virginia to reveal the names of the other Internet companies from whom the Justice Department solicited information about the three people: Jacob Appelbaum, an American citizen; Birgitta Jonsdottir of Iceland; and Rop Gonggrijp of the Netherlands.

Their case has become a testing ground for online privacy and speech, in part because the Justice Department sought the information without a search warrant in 2010. Instead, it relied on a 1994 law called the Stored Communications Act, and asked Twitter to release information about the three Twitter users. It sought, among other things, their Internet Protocol addresses, which identify and can give the location of a computer used to log onto the Internet. Twitter responded by informing the three about the government’s request – and they, in turn, went to court.

The petitioners argued that their I.P. addresses should be considered private information, and that this was unrelated to WikiLeaks. A federal judge in Virginia, Liam O’Grady, ruled against them last November, saying that the information sought by the government was relevant to a continuing ongoing investigation. The court also dismissed a petition to unseal the Justice Department’s explanation for why it sought the account information.

Earlier in January, the same judge refused to suspend the order pending an appeal, which meant that Twitter was required to furnish the data to the government.

The only other window into the Justice Department’s strategy came from a small Internet service provider in Northern California called Sonic.net. It too received a request from the Justice Department for information on Mr. Appelbaum, one of its customers. Sonic successfully went to court so it could inform Mr. Appelbaum of the government’s request.

The brief filed Friday seeks to unseal court orders sent to other companies seeking information about the three people. Aden Fine, an attorney with the A.C.L.U., said in a statement, “This case is just one example of the unfortunate recent trend to make our court processes less open and transparent.”