Cactus Ransomware Group Targets Fenwick Elliot

Cactus ransomware group claimed an attack against Fenwick Elliot. The group obtained several pieces of confidential corporate data. Fenwick Elliot is the largest construction and energy law firm in the UK, offering a full range of legal services for construction, engineering and energy projects worldwide.

Cactus's Modus Operandi

Cactus has been in operation since at least March 2023. Cactus has been observed employing known vulnerabilities within VPN appliances to initiate an initial breach. Once gaining entry to the network, Cactus operators engage in activities such as enumerating local and network user accounts and identifying accessible endpoints. They then proceed to generate new user accounts and utilize custom scripts for the automated rollout and activation of the ransomware encryptor through scheduled tasks.

Unique Encryption Method

It is noteworthy that the ransomware encryptor utilized by Cactus exhibits a unique characteristic – it necessitates a decryption key for the execution of the binary, likely implemented to evade detection by anti-virus software. This decryption key is concealed within a file containing random text named ntuser.dat, which is loaded through a scheduled task.