The researchers found that the creators of REvil deceived their partners using a scheme that allowed them to decrypt any systems blocked by the ransomware and take the entire ransom for themselves.
Their partners ended up with nothing.
Let me remind you that REvil (aka Sodinokibi) has existed since 2019 and is considered to be the heir of the GandCrab ransomware. The ransomware operates according to the Ransomware-as-a-Service (RaaS, ransomware-as-a-Service) scheme, that is, malware developers deal directly with malware and payment sites, and their hired partners hack victims’ networks and encrypt devices. As a result, the ransom payments are distributed between the hack group itself and its partners, with the latter usually receiving 70-80% of the total.
Evgeny Boguslavsky, a specialist at Advanced Intel, told reporters that since at least 2020, there have been rumours on hacker forums that the creators of REvil often negotiate with victims in secret chats, while their partners do not even know about it. These rumours began to appear more often after the sudden disappearance of the ransomware DarkSide and Avaddon (the operators of the latter generally published decryption keys for their victims).
According to Boguslavsky, REvil administrators sometimes create a second chat, identical to the one that their partners use to negotiate with the victim. When negotiations reach a critical point, the creators of REvil step in and portray a victim who supposedly abruptly breaks off negotiations, refusing to pay the ransom. In fact, the REvil authors themselves continue negotiations with the victims, take the entire ransom and leave their partners with nothing.
Recently, these rumours have become more substantiated, as the reverse engineer reported on hack forums that the REvil malware, which RaaS operators provide to their partners for deployment on victims’ networks, contains a “cryptobackdoor”. The discovery came after Bitdefender released a versatile tool to decrypt data after the REvil attacks.
Interestingly, full control over what is happening and the ability to decrypt any system is a practice that other ransomware uses as well. So, Boguslavsky says that, according to rumours, the DarkSide operators worked the same way. After rebranding to BlackMatter, the attackers openly announced this practice, making everyone understand that they reserve the right to take over negotiations at any time without giving any reason.
The head of Advanced Intelligence, Vitaly Kremez, told Bleeping Computer that the latest REvil samples that have appeared recently, after the group restored activity, no longer has a master key that would allow decrypting any system that was blocked by REvil.