(CNN) - The Justice Department alleged Wednesday that Russia has continued pushing online disinformation to discredit the American government, after a pro-Russian Twitter account spread confidential information from a criminal case that special counsel Robert Mueller's team brought against a Russian company for social media conspiracy.
The development highlights just how tense the standoff has become between US law enforcement and the Russian operation accused of interfering in the 2016 election.
The situation stems from terabytes of data in the criminal case against Russian company Concord Management and Consulting, which is accused of funding a social media effort aimed at swaying American voters in 2016. The Justice Department has been turning over evidence to Concord's US-based legal team, who can review it with a limited number of people as they fight the case.
Prosecutors now allege that some of the information turned over to Concord before trial got out in October -- after a now-suspended Twitter user touted that it had a "Mueller database" and a computer with a Russian IP address published thousands of documents online.
More than a thousand of those documents were part of the case's evidence collection, and were listed online under labels and folders known only to those involved in the case, the prosecutors said.
Other documents published online and mixed in with the real evidence were "junk material," prosecutors said.
"Certain non-sensitive discovery materials in the defense's possession appear to have been altered and disseminated as part of a disinformation campaign aimed (apparently) at discrediting ongoing investigations into Russian interference in the U.S. political system," the prosecutors wrote Wednesday.
The pro-Russia Twitter account at the center of Wednesday's filing first reached out to a CNN reporter in a private message in October. Reporters at other news organizations received a similar message.
"We are anonymous hackers. We are like hundreds of others, but we are the one and only who got the Special Counsel Mueller database," the message from @HackingRedstone read. "We got into a Russian lawyer company local net that had permission from ReedSmith (Russian attorneys) to view and download all the files they need from their database through the remove server. You might wonder why we want to share all of this information with you. So, you're just one of the few who can handle it in the right way. You are the one who can tell people the truth!"
While the reporter did not respond to the message, CNN did seek to find out from special counsel and the defense team if they had been hacked.
In late October, @HackingRedstone shared a webpage on Twitter that led to the documents from the criminal case.
Prosecutors didn't say in their filing Wednesday how the documents got online.
The law firm Reed Smith, which represents Concord, said in a statement Wednesday that it was "confident" the firm had not been hacked, nor did its members violate the court order prohibiting the spread of case files.
"We maintain the highest levels of security and protection for all of our systems and their contents," the law firm said. "Reed Smith has never hosted or maintained any of the data at issue here produced by the government in the Concord case on Reed Smith computer systems. A third-party vendor has hosted all such data and has assured us that there has been no breach of the database that maintains the data."
The evidence shared online was what prosecutors call "non-sensitive" and included information available elsewhere on the internet, like public posts that Concord's conspirators allegedly put on social media sites in 2016.
Yet other evidence, which was not leaked to the public, is so sensitive that sharing it with even a limited number of Russians could expose American national security secrets, prosecutors have argued. The prosecutors especially don't want the oligarch Yevgeny Prigozhin, who is charged in the case and owned Concord, to have access, according to several court filings.
So far, a federal judge has allowed the Justice Department to keep the information locked down so it can't be shared with others outside the case. The sensitive evidence is kept on computers disconnected from the internet.
But Concord says it needs to share documents in the case with Russians, including Prigozhin, as it prepares for trial and the US-based lawyers translate much of it from Russian.
But the prosecutors have pushed back. "Concord's request to send the sensitive discovery to the Russian Federation unreasonably risks the national security interests of the United States," the prosecutors wrote Wednesday.
Instead, the prosecutors suggest Prigozhin come to the US to face his charges and review the evidence.
The Justice Department points out in its filing Wednesday that "individuals and entities" engaging in the disinformation campaign still haven't been charged in the case. In previous court documents, prosecutors have said a federal grand jury continues to work on a matter related to Concord, suggesting that more indictments could come.
The prosecutors use the breadth of the online activity to argue that sensitive materials in the case shouldn't be shared more widely.
The sensitive materials disclose "sources, methods, and techniques used to identify the foreign actors behind these interference operations."
Handing that information to Russians would allow their "country to learn of these techniques and adjust their conduct, thus undermining US national security interests, including investigations into the conducts of these foreign actors," the filing said.
Concord's 13 alleged co-conspirators, who are all Russian, haven't appeared in US court, and are unlikely to be extradited to the US to face their charges.
If it were Russians who spread the evidence online, they also likely won't be punished, prosecutors said.