REvil Ransomware infects network of diagnostics corporation Grupo Fleury

REvil Ransomware has struck the healthcare industry once again, infecting the network of healthcare giant Grupo Fleury, an attack that disrupted business operations and forced company systems offline. Grupo Fleury is a Brazilian healthcare company founded in 1926, whose main activity is the provision of medical services and diagnostic medicine. With around 60 million exams performed in 2016, it is the second-largest company in the area in Brazil. The company has 200 service centers and more than 10,000 employees in the region.

Since the attack, the Fleury website displayed an alert stating that they suffered an attack and systems were not accessible.

“Please be advised that our systems are currently unavailable and that we are prioritizing the restoration of services. The causes of this unavailability originated from the attempted external attack on our systems, which are having operations reestablished with all the resources and technical efforts for the rapid standardization of our services.” read the alert translated into English.

Due to the REvil Ransomware infection, patients are unable to schedule tests, be they lab or clinical.

While local media has received confirmation that the company has suffered a cyberattack, Grupo Fleury has not officially confirmed a ransomware attack. However, many independent cybersecurity researchers have been analyzing the incident, and researchers at BleepingComputer have confirmed it is a REvil Ransomware infection.

This ransomware operation is responsible for numerous high-profile attacks, including Brazil’s Rio Grande do Sul court system, nuclear weapons contractor Sol Oriens, and JBS, the world’s largest meat producer.

In the sample BleepingComputer is working with, it is believed that the ransom demanded by the gang in this case is $5 Million.

REvil is known for stealing files before encrypting devices and then using the stolen data as leverage to get a company to pay the ransom.

From the ransomware sample, no proof of stolen data or mention of the victim’s name has been shared by the attackers at this time.

If data has been stolen, Grupo Fleury’s data is of significant concern as it could contain enormous amounts of personal and medical data of patients.

REvil Ransomware Analysis

REvil Ransomware is a Ransomware-as-a-Service (RaaS), meaning it can be sold on a subscription basis and is usable by just about anybody. In 2020, it extorted large amounts of money for corporations and individuals. According to researchers, it is the most widespread ransomware strain. Groups using have a knack for shaking down businesses that don’t meet their demands, often through threats or leaking dating.

REvil Ransomware, also known as Sodinokibi, first appeared in April 2019 and rose to prominence after another RaaS gang called GandCrab shut down its service. REvil was first advertised on Russian-language cybercrime forums. The main actor associated with advertising and promoting REvil ransomware is called Unknown aka UNKN.  In the early days of REvil, researchers and security firms identified it as a strain of GandCrab, or at least established multiple links between the two. An alleged member of the group, using the handle Unknown, confirmed in an interview that the ransomware was not a new creation and that it was built on top of an older codebase that the group acquired.

The group behind REvil Ransomware and other groups selling RaaS often do so on a commission basis. Usually, this means a cut of between 20% and 30% of the money earned through infecting victims with ransomware.

In 2020, the IBM Security X-Force Incident Response reported that 1 in 3 Ransomware infections were caused by REvil Ransomware.

In February 2021, the REvil ransomware operation posted a job notice where they were looking to recruit people to perform DDoS attacks and use VOIP calls to contact victims and their partners.

In March, a security researcher known as 3xp0rt discovered that REvil has announced that they were introducing new tactics that affiliates can use to exert even more pressure on victims.

These new tactics include a free service where the threat actors, or affiliated partners, will perform voice-scrambled VOIP calls to the media and victim’s business partners with information about the attack. The ransomware gang is likely assuming that warning businesses that their data may have been exposed in an attack on of their partners, will create further pressure for the victim to pay.

REvil Ransomware is also providing a paid service that allows affiliates to perform Layer 3 and Layer 7 DDoS attacks against a company for maximum pressure. A Layer 3 attack is commonly used to take down the company’s Internet connection. In contrast, threat actors would use a Layer 7 attack to take down a publicly accessible application, such as a web server.

It is highly configurable, and it can be customized to behave differently depending on the host. This makes it a highly attractive RaaS client. Some of its features include:

• Exploits a kernel privilege escalation vulnerability to gain SYSTEM privileges using CVE-2018-8453.
• Whitelists files, folders and extensions from encryption.
• Kills specific processes and services prior to encryption.
• Encrypts files on local and network storage.
• Customizes the name and body of the ransom note, and the contents of the background image.
• Exfiltrates encrypted information on the infected host to remote controllers.
• REvil Ransomware uses Hypertext Transfer Protocol Secure (HTTPS) for communication with its controllers.

REvil ransomware exploits a kernel privilege escalation vulnerability in win32k.sys tracked as CVE-2018-8453 to gain SYSTEM privileges on the infected host. If the configuration instructs a sample to execute this exploit, it will allocate executable memory, decrypt the exploit code in the newly allocated region and invoke it.