The Special Counsel’s office said in a court filing Wednesday that 1,000 sensitive files handed over during discovery to defense lawyers for the Russian company Concord Management—which is charged with financing interference efforts in the 2016 presidential election—were subsequently altered and released online “as part of a disinformation campaign aimed (apparently) at discrediting ongoing investigations into Russian interference in the U.S. political system.” The filing comes as part of Mueller’s effort to continue to restrict access to documents in the case against Concord, which has asked the court to allow it to share thousands of sensitive digital documents with company officers in Russia.

Mueller cited an October 2018 breach of the protective order placed on the discovery process where a newly created, Russia-linked Twitter account @HackingRedstone tweeted out: “We’ve got access to the Special Counsel Mueller’s probe database as we hacked Russian server with info from the Russian troll case Concord LLC v. Mueller. You can view all the files Mueller had about the IRA and Russian collusion. Enjoy the reading!” The tweet included a link to a page that Mueller says included sensitive discovery documents that were structured in such a way that made it clear they were obtained after the Russia investigation had begun (and were not hacked before) and were not hacked from U.S. government computers. That leaves the defense team for Concord as the likely leak because the documents were only accessible under very narrow parameters, namely at the U.S. law offices of the firm representing Concord in the matter, Reed Smith LLP.

From the filing:

The protective order barred any individual or entity—including Concord officer Yevgeniy Prigozhin—other than the U.S. defense team from accessing, sharing, or discussing sensitive discovery materials absent the Court’s approval. The order further required that sensitive discovery materials be stored offline at the U.S. offices of Reed Smith LLP (“Reed Smith”) and not be disclosed, transported, or transmitted outside the United States. The order also required that any person reviewing sensitive materials must be accompanied at all times by a designated and identified employee of a U.S. office of Reed Smith.

Prosecutors stopped short of accusing Concord’s legal team of leaking the documents; Reed Smith notified the special counsel the day after the tweet that they had received inquiries from journalists about the tweet and the content it linked to. The special counsel instead used the incident to reassert in court that allowing a company controlled by Yevgeny Prigozhin, a wealthy businessman known as ‘Putin’s chef’ who has been sanctioned and charged by the U.S. government to control sensitive documents pertaining to the Russia investigation was as bad an idea as it sounds. “The sensitive discovery identifies uncharged individuals and entities that the government believes are continuing to engage in operations that interfere with lawful U.S. government functions like those activities charged in the indictment,” Mueller’s team said in the filing. “[I]nformation within the sensitive discovery identifies sources, methods, and techniques used to identify the foreign actors behind these interference operations.”