The FBI, CISA, and the U.S. Treasury Department are warning that North Korean state-sponsored hackers are using ransomware to target healthcare and public health sector organizations across the United States.
In a joint advisory published Wednesday, the U.S. government agencies said they had observed North Korean-backed hackers deploying Maui ransomware since at least May 2021 to encrypt servers responsible for healthcare services, including electronic health records, medical imaging, and entire intranets.
“The FBI assesses North Korean state-sponsored cyber actors have deployed Maui ransomware against Healthcare and Public Health Sector organizations,” the advisory reads. “The North Korean state-sponsored cyber actors likely assume healthcare organizations are willing to pay ransoms because these organizations provide services that are critical to human life and health. Because of this assumption, the FBI, CISA, and Treasury assess North Korean state-sponsored actors are likely to continue targeting [healthcare] organizations.”
The advisory notes that in many of the incidents observed and responded to by the FBI, the Maui ransomware caused disruption to healthcare services “for prolonged periods.”
Maui was first identified by Stairwell, a threat-hunting startup that aims to help organizations determine if they have been compromised, in early-April 2022. In an analysis of the ransomware, Stairwell principal reverse engineer Silas Cutler notes that Maui lacks many of the features commonly seen with tooling from ransomware-as-a-service (RaaS) providers, such as an embedded ransom note or automated means of transmitting encryption keys to attackers. Rather, Stairwell concludes that Maui is likely manually deployed across victims’ networks, with remote operators targeting specific files they want to encrypt.
North Korea has long used cryptocurrency-stealing operations to fund its nuclear weapons program. In an email, John Hultquist, vice president of Mandiant Intelligence, said that as a result “ransomware is a no-brainer” for the North Korean regime.
“Ransomware attacks against healthcare are an interesting development, in light of the focus these actors have made on this sector since the emergence of COVID-19. It is not unusual for an actor to monetize access which may have been initially garnered as part of a cyber espionage campaign,” said Hultquist. “We have noted recently that North Korean actors have shifted focus away from healthcare targets to other traditional diplomatic and military organizations. Unfortunately, healthcare organizations are also extraordinarily vulnerable to extortion of this type because of the serious consequences of a disruption,” he added.
The advisory, which also includes indicators of compromise (IOCs) and information on tactics, techniques and procedures (TTPs) employed in these attacks to help network defenders, urges organizations in the healthcare industries to strengthen their defenses by limiting access to data, turning off network device management interfaces, and by using monitoring tools to observe whether Internet of Things devices have become compromised.
“The FBI, along with our federal partners, remains vigilant in the fight against North Korea’s malicious cyber threats to our healthcare sector,” said FBI Cyber Division assistant director Bryan Vorndran. “We are committed to sharing information and mitigation tactics with our private sector partners to assist them in shoring up their defenses and protecting their systems.”
The U.S. government’s latest warning follows a spate of high-profile cyberattacks targeting healthcare organizations; University Medical Center Southern Nevada was hit by a ransomware attack in August 2021 that compromised files containing protected health information and personally identifiable information, and Eskenazi Health said in October that cybercriminals had access to their network for almost three months. Last month, Kaiser Permanente confirmed a breach of an employee’s email account led to the theft of 70,000 patient records.