A new variant of Cicada ransomware targets VMware ESXi systems

A new ransomware-as-a-service (RaaS) operation called Cicada3301 has emerged in the threat landscape and already targeted tens of companies.

Cicada3301 is a new ransomware-as-a-service (RaaS) operation that appeared in the threat landscape. The group appears to be very active and already listed 23 victims on its extortion portal since mid-June. The following image shows the list of victims published by the gang on its Dark Web leak site.

Cicada 3301 is the name given to three sets of puzzles posted under the name “3301” online between 2012 and 2014. The first puzzle started on January 4, 2012, on 4chan and ran for nearly a month. A second round of puzzles began one year later on January 4, 2013, and then a third round following the confirmation of a fresh clue posted on Twitter on January 4, 2014. The third puzzle has not been solved yet. The stated intent was to recruit “intelligent individuals” by presenting a series of puzzles to be solved; no new puzzles were published on January 4, 2015.

However, the operation seems to have no links with Cicada3301.

Since June, the operators behind Cicada3301 have started recruiting affiliates on the RAMP cybercrime forum.

The Cicada3301 ransomware is written in Rust and targets both Windows and Linux/ESXi hosts. Truesec researchers dissected a variant that targets VMware ESXi systems, which appears to be a version of the same malware for Windows. The experts pointed out that while many ransomware groups are now targeting ESXi systems, only a few, including the now-defunct BlackCat/ALPHV group, have used Rust-based ransomware. Analysis reveals significant similarities between Cicada3301’s ransomware and the ALPHV ransomware.

“The Cicada3301 ransomware has several interesting similarities to the ALPHV ransomware.” reported Truesec.

• Both are written in Rust
• Both use ChaCha20 for encryption
• Both use almost identical commands to shutdown VM and remove snapshots[1]
• Both use –ui command parameters to provide a graphic output on encryption
• Both use the same convention for naming files, but changing “RECOVER-“ransomware extension”-FILES.txt”  to “RECOVER-“ransomware extension”-DATA.txt”[2]
• How the key parameter is used to decrypt the ransomware note

The initial attack by the Cicada3301 group began with the use of stolen or brute-forced credentials to log in via ScreenConnect. The IP address used by the ransomware group is linked to the Brutus botnet, a circumstance that suggests possible connections between the two. This timeline coincides with the apparent exit of the BlackCat/ALPHV ransomware group, raising the possibility that Cicada3301 could be a rebranding of ALPHV, a collaboration with its developers, or a separate group using modified ALPHV code.

The Cicada3301 ransomware supports multiple configurable parameters that operators can use to alter its behavior during the execution. These parameters, managed via the clap::args library, include options like:

• sleep: Delays execution of the ransomware by a specified number of seconds.
• ui: Displays real-time progress and statistics of the encryption process, such as the number of files encrypted.
• no_vm_ss: Encrypts files on ESXi hosts without shutting down running virtual machines, using the esxicli terminal and deleting snapshots.

These functionalities provide flexibility in how the ransomware operates, potentially making it more effective in different scenarios.

The Cicada3301 ransomware generates a symmetric key for encryption using the OsRng random number generator. The ransomware uses a function called encrypt_file to handle file encryption. This process involves extracting a public PGP key stored in the binary’s data section, which is used to encrypt the generated symmetric key.

Then the malware creates a note titled “RECOVER-[encrypted file ending]-DATA.txt” in each folder containing encrypted files. The encryption targets specific file extensions, mostly related to documents and pictures, suggesting the ransomware was initially designed to target Windows systems before being adapted for ESXi hosts.

“After the encryption is done, the ransomware encrypts the ChaCha20 key with the provided RSA key and finally writes the extension to the encrypted file. Adding the encryption file extension The file extension is also added to the end of the encrypted file together with the RSA encrypted ChaCha20 key.” concludes the analysis that includes YARA Rule for this version of the malware
Pierluigi Paganini

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(SecurityAffairs – hacking, Cicada3301)