Threat Signal Report

Meet Rook Ransomware

description-logo Description

FortiGuard Labs is aware of a recently reported ransomware "Rook". According to a publicly available report, Rook appears to be based on the leaked Babuk ransomware source code. One of the Rook's victims is a financial institution in Kazakhstan which the ransomware gang stole more than 1,000 GB worth of data.

Why is this Significant?

This is significant because Rook is one of the recent ransomware gangs that joined the already crowded ransomware landscape. The ransomware reportedly infected a financial institution in Kazakhstan and stole more than 1,000 GB worth of data.

What is Rook Ransomware?

Rook ransomware is reported to be based on the leaked Babuk source code and was first discovered in the wild at the end of November 2021. Files encrypted by Rook ransomware typically has ".rook" file extension, however the earlier version of Rook is said to use ".tower" file extension instead. The ransomware leaves a ransom note in HowToRestoreYourFiles.txt, which the victim is instructed to contact the Rook gang by either accessing the Rook's Tor web site or emailing the threat actor. The ransom note warns the victim that the private key to decrypt the encrypted files will be destroyed if a security vendor or law enforcement agency joins the negotiation.

How is Rook Ransomware Delivered?

Rook ransomware is reported to have been delivered via Cobalt Strike or untrustworthy Torrent downloads.

What is the Status of Coverage?

FortiGuard Labs provide the following AV coverage against Rook ransomware:



Traffic Light Protocol

Color When Should it Be used? How may it be shared?


Not for disclosure, restricted to participants only.
Sources may use TLP:RED when information cannot be effectively acted upon by additional parties, and could lead to impacts on a party's privacy, reputation, or operations if misused. Recipients may not share TLP:RED information with any parties outside of the specific exchange, meeting, or conversation in which it was originally disclosed. In the context of a meeting, for example, TLP:RED information is limited to those present at the meeting. In most circumstances, TLP:RED should be exchanged verbally or in person.


Limited disclosure, restricted to participants’ organizations.
Sources may use TLP:AMBER when information requires support to be effectively acted upon, yet carries risks to privacy, reputation, or operations if shared outside of the organizations involved. Recipients may only share TLP:AMBER information with members of their own organization, and with clients or customers who need to know the information to protect themselves or prevent further harm. Sources are at liberty to specify additional intended limits of the sharing: these must be adhered to.


Limited disclosure, restricted to the community.
Sources may use TLP:GREEN when information is useful for the awareness of all participating organizations as well as with peers within the broader community or sector. Recipients may share TLP:GREEN information with peers and partner organizations within their sector or community, but not via publicly accessible channels. Information in this category can be circulated widely within a particular community. TLP:GREEN information may not be released outside of the community.


Disclosure is not limited.
Sources may use TLP:WHITE when information carries minimal or no foreseeable risk of misuse, in accordance with applicable rules and procedures for public release. Subject to standard copyright rules, TLP:WHITE information may be distributed without restriction.