Security researchers reverse engineered the updated GandCrab ransomware and discovered new features that improve its ability to evade detection and impede analysis by defense teams.
First discovered in January, GandCrab is now the most powerful threat of its kind, whether directed at a single person or an entire company, according to a July 31 threat report from McAfee.
GandCrab is similar to its peers in that it dupes users into installing it, locks them out of their devices and demands payment in cryptocurrency before restoring access. These new ransomware attacks can be introduced through a variety of attack vectors, from traditional phishing emails to Trojans, fake programs and exploit kits.
New Ransomware Attacks Hiding in Layers of Encryption
While a series of bugs in GandCrab’s code suggests that the ransomware isn’t the work of professionals, according to the researchers, it has unique characteristics that should put security teams on high alert. The most recent versions, for example, use an algorithm called Salsa20 to encrypt files instead of slower and less efficient alternatives such as the Advanced Encryption Standard (AES) and RSA.
By generating random Salsa20 keys and initialization vectors for each file, GandCrab essentially guards itself with a series of encryption layers that prevent victims from breaking it open again. Security teams would need a private key to get at the embedded public key. In addition, since GrandCrab deletes itself and any “shadow volumes” that might otherwise remain on an infected device, it is difficult for researchers to learn about new ransomware attacks after the fact.
Defend Your Data With Last Resort Containment
Given how quickly this ransomware has become valuable to cybercriminals and the promotion it may be getting on underground forums, it may not always be possible to shut GandCrab out of corporate networks. In its “Ransomware Response Guide,” IBM X-Force recommends a method called last resort containment to help organizations respond when they can’t quickly or easily figure out where new ransomware attacks are coming from.
Steps to consider in this process include shutting down all file shares, taking them offline and restricting them by network. This can help decrease the likelihood that the ransomware will encrypt the shares and help businesses avoid paying fees to recover their stolen files.
Writer & Editor
Shane Schick is a contributor for SecurityIntelligence.