Written by Jeff Stone

A group of hackers has released documents stolen from high-profile firms allegedly detailing litigation and real-estate development deals after the September 11, 2001 terrorist attacks.

The Dark Overlord, a hacking group known for breaching entertainment companies and harassing U.S. school systems, said Wednesday it released “a small sample of documents” to verify prior claims that the group breached international firms. In a Dec. 31 Pastebin post, the group said it hacked New York-based real estate developer Silverstein Properties along with insurers Hiscox Syndicates and Lloyds of London to find sensitive security information tied to the 9/11 attacks. The group also claims it obtained classified material from U.S. agencies including the FBI, the Department of Justice, the Federal Aviation Administration and others.

The files, released Wednesday with access instructions and a decryption key, includes various documents and powerpoint presentations tied to liability cases regarding the World Trade Center attacks. The documents refer to cases that were open as of 2003, and contain contributions from people who were Hiscox and Lloyd’s employees at the time.

“This story isn’t about insurance litigation so much as it’s about highly sensitive [special compartment information] and [sensitive security information] that details security procedures, defence operations, law enforcement investigations, evidence materials, and more that was never publicly released due to its sensitive nature,” the Dark Overlord said in a tweet.

The Hiscox Group confirmed to Motherboard that a law firm which advised the company had been breached, and that thieves likely stole files about 9/11 litigation. Silverstein, in a statement Wednesday to CyberScoop, said it has “found no evidence to support a security breach at our company.” A Lloyd’s spokesperson said the company “has found no evidence to suggest” its networks or systems have been compromised.

The files are a preview collection of a possible five installments The Dark Overlord has offered to release this week in exchange for bitcoin. A file of the most sensitive documents, which the group says contains information classified at the Top Secret level, will be released for $2,000,000 in bitcoin. The cheapest installment will be released for $5,000 in bitcoin, the group says.

“The financial requests have been adjusted for the general public,” the Dark Overlord said in an email Wednesday to CyberScoop. “We’re unwilling to disclose specifics, but we’ve been permitted to disclose that we’re in negotiations with particular parties who are involved in the documents.”

The bitcoin wallet where the group is asking for payment has received three transactions as of this article’s publication.

The Dark Overlord is perhaps best known for a series of 2017 hacks that made international headlines. The hackers attacked the production company Larson Studios, stealing unseen episodes of the popular show “Orange is the New Black” and demanding a ransom payment. Despite receiving a payment of roughly $50,000, the hackers still leaked the episodes as retaliation for Larson contacting the FBI, they told Variety magazine.

In another case, the Dark Overlord hackers said they sent threatening messages to schools, students and parents, forcing school closures in Iowa and Montana.

Last May, law enforcement in Serbia claimed to have arrested a member of the hacking syndicate in an “international operation conducted by the FBI.” The group claimed shortly after the arrest that it would continue its operations unabated.

Greg Otto contributed to this report.