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With version 4, GandCrab ransomware has undergone a major overhaul, adding an NSA exploit to help spread and targeting a larger set of systems.
The updated GandCrab ransomware was first discovered earlier this month, but researchers are just now learning the extent of the changes. The code structure of the GandCrab ransomware was completely rewritten. And, according to Kevin Beaumont, a security architect based in the U.K., the malware now uses the EternalBlue National Security Agency (NSA) exploit to target SMB vulnerabilities and spread faster.
"It no longer needs a C2 server (it can operate in airgapped environments, for example) and it now spreads via an SMB exploit -- including on XP and Windows Server 2003 (along with modern operating systems)," Beaumont wrote in a blog post. "As far as I'm aware, this is the first ransomware true worm which spreads to XP and 2003 -- you may remember much press coverage and speculation about WannaCry and XP, but the reality was the NSA SMB exploit (EternalBlue.exe) never worked against XP targets out of the box."
Joie Salvio, senior threat researcher at Fortinet, based in Sunnyvale, Calif., found the GandCrab ransomware was being spread to targets via spam email and malicious WordPress sites and noted another major change to the code.
"The biggest change, however, is the switch from using RSA-2048 to the much faster Salsa20 stream cipher to encrypt data, which had also been used by the Petya ransomware in the past," Salvio wrote in the analysis. "Furthermore, it has done away with connecting to its C2 server before it can encrypt its victims' file, which means it is now able to encrypt users that are not connected to the Internet."
The GandCrab ransomware appears to specifically avoid targeting users in Russian-speaking regions. Fortinet found the malware will abort if it finds a system using the Russian keyboard layout.
Despite the overhaul of the GandCrab ransomware and the expanded systems being targeted, Beaumont and Salvio both said basic cyber hygiene should be enough to protect users from attack. This includes installing the EternalBlue patch released by Microsoft, keeping antivirus up-to-date and disabling SMB version 1 altogether, which is advice that has been repeated by various outlets, including US-CERT, since the initial WannaCry attacks began.