Black Basta, a new ransomware group has been highly active since April 2022 and has already breached a dozen companies worldwide. The list of victims includes the American Dental Association and German wind turbine giant Deutsche Windtechnik.
Modus operandi of Black Basta
While Black Basta assaults are relatively new, some information on their methodology has been made public. The data encryptor employed by ransomware requires administrator privileges to execute, otherwise, it is harmless.
To launch the encryption executable, the ransomware targets a legitimate Windows service. After execution, the ransomware erases shadow copies from the compromised system using vssadmin.exe. This action removes the Windows backup so that after encryption victim cannot revert the system to its previous state.
Subsequently, Black Basta drops two files: dlaksjdoiwq.jpg and fkdjsadasd.ico in the user Temp folder. The second file is a custom icon for all files with the “.basta” extension. The icon is assigned by designing and setting a new registry key “HKEY_CLASSES_ROOT\.basta\DefaultIcon”.
The persistence technique of the Black Basta ransomware is executed by “stealing” an existing service name, deleting the service, and then creating a new service named ‘FAX. Before the encryption routine begins, the ransomware checks the boot options using GetSystemMetrics() API and then adds HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\Fax entry in the registry to start the FAX service in safe mode.
After completing all the customizations, the ransomware sets up the operating system to boot in safe mode using bcedit.exechecks. Due to the reboot mode change, the PC will reboot in safe mode with the ‘Fax’ service running. This service will then execute the ransomware again, but this time for the purpose of encryption.
Methodologies Identical to Conti group
Researchers at MalwareHunterTeam attribute the Black Basta ransomware to the team behind Conti ransomware. This assumption is based on similarities between their leak sites, their payment sites, and the way their “support” employees talk and behave.
Lawrence Abrams of BleepingComputer also mentioned that the threat actors behind Black Basta seem like they are exerting a lot of effort to avoid any resemblance to their previous identity.
To prevent Black Basta ransomware from further encryptions, it must be eliminated from the operating system. Unfortunately, removal will not restore already compromised data. The sole solution is recovering it from a backup if one was created beforehand and is stored elsewhere.
Additionally, to avoid permanent data loss, researchers recommend keeping backups in multiple different locations (e.g., remote servers, unplugged storage devices, etc.
