The U.S. Federal Bureau of Investigation (FBI) disclosed today that it infiltrated the world’s second most prolific ransomware gang, a Russia-based criminal group known as ALPHV and BlackCat. The FBI said it seized the gang’s darknet website, and released a decryption tool that hundreds of victim companies can use to recover systems. Meanwhile, BlackCat responded by briefly “unseizing” its darknet site with a message promising 90 percent commissions for affiliates who continue to work with the crime group, and open season on everything from hospitals to nuclear power plants.

A slightly modified version of the FBI seizure notice on the BlackCat darknet site (Santa caps added).

Whispers of a possible law enforcement action against BlackCat came in the first week of December, after the ransomware group’s darknet site went offline and remained unavailable for roughly five days. BlackCat eventually managed to bring its site back online, blaming the outage on equipment malfunctions.

But earlier today, the BlackCat website was replaced with an FBI seizure notice, while federal prosecutors in Florida released a search warrant explaining how FBI agents were able to gain access to and disrupt the group’s operations.

A statement on the operation from the U.S. Department of Justice says the FBI developed a decryption tool that allowed agency field offices and partners globally to offer more than 500 affected victims the ability to restore their systems.

“With a decryption tool provided by the FBI to hundreds of ransomware victims worldwide, businesses and schools were able to reopen, and health care and emergency services were able to come back online,” Deputy Attorney General Lisa O. Monaco said. “We will continue to prioritize disruptions and place victims at the center of our strategy to dismantle the ecosystem fueling cybercrime.”

The DOJ reports that since BlackCat’s formation roughly 18 months ago, the crime group has targeted the computer networks of more than 1,000 victim organizations. BlackCat attacks usually involve encryption and theft of data; if victims refuse to pay a ransom, the attackers typically publish the stolen data on a BlackCat-linked darknet site.

BlackCat formed by recruiting operators from several competing or disbanded ransomware organizations — including REvil, BlackMatter and DarkSide. The latter group was responsible for the Colonial Pipeline attack in May 2021 that caused nationwide fuel shortages and price spikes.

Like many other ransomware operations, BlackCat operates under the “ransomware-as-a-service” model, where teams of developers maintain and update the ransomware code, as well as all of its supporting infrastructure. Affiliates are incentivized to attack high-value targets because they generally reap 60-80 percent of any payouts, with the remainder going to the crooks running the ransomware operation.

BlackCat was able to briefly regain control over their darknet server today. Not long after the FBI’s seizure notice went live the homepage was “unseized” and retrofitted with a statement about the incident from the ransomware group’s perspective.

The message that was briefly on the homepage of the BlackCat ransomware group this morning. Image: @GossiTheDog.

BlackCat claimed that the FBI’s operation only touched a portion of its operations, and that as a result of the FBI’s actions an additional 3,000 victims will no longer have the option of receiving decryption keys. The group also said it was formally removing any restrictions or discouragement against targeting hospitals or other critical infrastructure.

“Because of their actions, we are introducing new rules, or rather, we are removing ALL rules except one, you cannot touch the CIS [a common restriction against attacking organizations in Russia or the Commonwealth of Independent States]. You can now block hospitals, nuclear power plants, anything, anywhere.”

The crime group also said it was setting affiliate commissions at 90 percent, presumably to attract interest from potential affiliates who might otherwise be spooked by the FBI’s recent infiltration. BlackCat also promised that all “advertisers” under this new scheme would manage their affiliate accounts from data centers that are completely isolated from each other.

BlackCat’s darknet site currently displays the FBI seizure notice. But as BleepingComputer founder Lawrence Abrams explained on Mastodon, both the FBI and BlackCat have the private keys associated with the Tor hidden service URL for BlackCat’s victim shaming and data leak site.

“Whoever is the latest to publish the hidden service on Tor (in this case the BlackCat data leak site), will resume control over the URL,” Abrams said. “Expect to see this type of back and forth over the next couple of days.”

The DOJ says anyone with information about BlackCat affiliates or their activities may be eligible for up to a $10 million reward through the State Department’s “Rewards for Justice” program, which accepts submissions through a Tor-based tip line (visiting the site is only possible using the Tor browser).

Further reading: CISA StopRansomware Alert on the tools, techniques and procedures used by ALPHV/BlackCat.