The filing is the latest in the legal wrangling between Mueller's team and Concord Management and Consulting, LLC, a Russian firm owned by Yevgeniy Prigozhin, a reported associate of Russian President Vladimir Putin.
A total of 13 Russians were also indicted along with Concord in the case, and as As CNN's Shimon Prokupecz also flagged in a tweet, the sensitive information involves "identifies uncharged individuals and entities that the government believes are continuing to engage in operations that interfere with lawful USA government functions like those activities charged in the indictment".
Eric Dubelier, a lawyer for Concord, did not immediately return a phone message seeking comment.
Earlier in the day, Mueller's team claimed in court that sensitive, non-public materials from one of the special counsel's indictments ended up on a public Russian server. His company Concord did hire U.S. lawyers, however, to fight the charges.
The special counsel alleges that "non-sensitive discovery materials have been misused in a manner inconsistent with the terms of" a protective order that the judge issued in the case. You can view all the files Mueller had about the [Internet Research Agency] and Russian collusion.
The filing was part of the Department of Justice's court fight to prevent Concord from sharing discovery information with those in the Russian Federation. "Enjoy the reading!" The tweet included a link to a webpage that contained file folder names and folder structure matching the material Mueller produced. Unique identifiers, or "hashtag values", for more than 1,000 files were found to match those of evidentiary files, which were mixed in randomly with "junk material", they said. It does not say how the special counsel thinks the material made its way online but notes that there is no evidence the special counsel or any government servers were hacked. The Mueller documents were largely "images of political memes from Facebook and other social media" that were posted during the 2016 election by the Internet Research Agency, a Russian social media troll farm.
The Russian firm, Concord Management and Consulting LLC, is being prosecuted in Mueller's investigation of United States allegations that Moscow meddled in 2016 to undermine the American democratic process and help then-Republican candidate Donald Trump defeat Democrat Hillary Clinton. Somewhat confusingly, the filing argued that many other file names used a reference to the Relativity database, which the USA government "has not used" to store materials related to this case.
The U.S. government warned that Concord's requests could jeopardize the secrecy of a grand jury matter and identify "uncharged individuals and entities that the government believes are continuing to engage" in interference operations like those Concord is charged with undertaking.
Concord Management is being prosecuted in Mueller's investigation of USA allegations that Moscow meddled in the American democratic process to help Trump defeat Democrat Hillary Clinton.