Security researchers from Cisco Talos discovered a new remote access Trojan (RAT) dubbed CannibalRAT that has been written entirely in Python.

The CannibalRAT RAT is being used in highly targeted attacks. the experts explained that even if it isn’t very sophisticated it exhibits signs of code cannibalisation from other open-source projects.

“The RAT itself is not very sophisticated, and exhibits signs of code cannibalisation from other open-source projects, which contrasts with the command-and-control, using fast flux to keep hidden, even if the endpoints are not very diversified.” reads the analysis published by Talos.

The researchers observed the involvement of at least two variants (versions 3.0 and 4.0) in targeted attacks.

The two samples were written using Python and packed into an executable using the popular tool py2exe.

According to the researchers, the version 4.0 is a stripped-down version, this means that vxers removed from the main code some features, anyway authors have attempted to add obfuscation techniques in order to avoid detection.

The version 4.0 includes a function that will generate random strings in memory in the attempt to make memory string analysis harder.

“The malware main script bytecode is stored in a portable executable (PE) section called PYTHONSCRIPT, while the Python DLL is stored in a section called PYTHON27.DLL. All the remaining modules’ bytecode is compressed and stored in the executable overlay.” continues the analysis.

The first variant of the malware was spotted on Jan. 8, anyway, Cisco Talos observed a significant increase in the activities of the CannibalRAT after the variant 4.0 appeared in the wild on February 5, 2018

Both variants use base16 encoding scheme to obfuscate command and control (C&C) hostnames and data exchanged with the server, they gain persistence by using “CurrentVersion\Run” registry key with the service name “Java_Update“,

Once executed, the CannibalRAT version 4.0 creates a PDF file with HTML code embedded that loads an image hosted at imgur.com and launches Chrome to open the PDF.

The two versions share the same C&C servers, but while the variant 3.0 uses standard web requests, the newer version uses a REST-based API.

“The command-and-control infrastructure attempts to use the fast flux technique to hide, although the name servers are changing with high frequency, and the end points tend to be the same, all belonging to a telecom provider in Brazil with the autonomous system number AS 7738 and shared among all four command-and-control hostnames.” states Cisco Talos.

CannibalRAT borrows the credential-stealer modules form the Radium-Keylogger, which has the source code published on Github, the experts also noticed that the VM detection feature was copied from a different Github repository.

“The malware’s modules have self-explanatory names: runcmd, persistence, download, upload, screenshot, miner, DDoS, driverfind, unzip, ehidden, credentials, file, zip, python, update, and vm.” continues the analysis.”All are present in version 3.0, while version 4.0 lacks the distributed denial of service, miner, Python and update modules, as well as the ability to steal credentials from Firefox (it only works with Chrome).”

Experts noticed that the version 4.0 doesn’t use modules, instead, all the code is included in the main script. Furthermore.

Talos team provided details of a campaign involving the CannibalRAT Version targeting the INESAP, a Brazilian school for public administration

The campaign is highly targeted at this specific geographic region, attackers targeted only Chrome users.

“the RAT was hosted at inesapconcurso.webredirect.org and filebin.net, while the second domain is a popular file-sharing platform, the first domain was clearly created as part of the campaign.” continues the analysis.

“The subdomain inesapconcurso is the aggregation of two words; inesap and concurso. The first word is the school name, the second can be translated into competition, this is part of the social engineering of this campaign, as this Institute helps the management the application of workers to public sector vacancies.”

Further info about the malware including IoCs are reported in the analysis.

Pierluigi Paganini

(Security Affairs – Russian hackers, Pyeongchang Olympic Games)

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