Threat Signal Report

Alert (AA22-181A) #StopRansomware: MedusaLocker

description-logo Description

FortiGuard Labs is aware that a joint Cybersecurity Advisory (CSA) on MedusaLocker ransomware was released by the Federal Bureau of Investigation (FBI), the Cybersecurity and Infrastructure Security Agency (CISA), the Department of the Treasury, and the Financial Crimes Enforcement Network (FinCEN). MedusaLocker infection typically occurs through Remote Desktop Protocol (RDP) compromise, propagates MedusaLocker throughout the network, and uses AES-256 encryption to encrypt files.

Why is this Significant?

This is significant as the joint Cybersecurity Advisory (CSA) is the latest #StopRansomware advisory released by the Federal Bureau of Investigation (FBI), the Cybersecurity and Infrastructure Security Agency (CISA), the Department of the Treasury, and the Financial Crimes Enforcement Network (FinCEN), which provides observed tactics, techniques, and procedures (TTPs) and indicators of compromise (IOCs) to help organizations protect against ransomware.

What is MedusaLocker Ransomware?

MedusaLocker is a ransomware that encrypts files in the compromised machines with the AES-256 encryption algorithm and demands victims to pay a ransom in order to recover the affected files. According to the advisory, MedusaLocker primarily takes advantage of an insecure RDP configuration as an initial infection vector, however email spam and malicious attachments are also used.

The advisory also states that MedusaLocker ransomware uses multiple infection processes:

  1. Uses a batch file to execute PowerShell script, which propagates the ransomware throughout the network.
  2. Restarts the LanmanWorkstation service, which allows registry edits to take effect.
  3. Kills the processes belonging to well-known security, accounting, and forensic software.
  4. Restarts the machine in safe mode.
  5. Encrypts files in the compromised machines with the AES-256 encryption algorithm
  6. Runs every 60 seconds, encrypting all files except those critical to the functionality of the victim's machine and those that have the designated encrypted file extension.
  7. Establishes persistence by copying an executable (svhost.exe or svhostt.exe) to the %APPDATA%\Roaming directory and scheduling a task to run the ransomware every 15 minutes.
  8. Attempts to prevent standard recovery techniques by deleting local backups, disabling startup recovery options, and deleting shadow copies.
  9. Leaves a ransom note into every folder containing instruction on how to reach out to the attacker either via MedusaLocker's Tor sites or emails.

The following is a list of known file extensions that MedusaLocker adds to the encrypts files:

  • .1btc
  • .bec
  • .cn
  • .datalock
  • .deadfilesgr
  • .decrypme
  • .encrypted
  • .faratak
  • .FartingGiraffeAttacks
  • .fileslock
  • .fileslocked
  • .key1
  • .lock
  • .lockdata7
  • .lockfiles
  • .lockfilesUS
  • .marlock01
  • .marlock02
  • .marlock08
  • .marlock11
  • .marlock13
  • .marlock25
  • .marlock6
  • .marlock011
  • .matlock20
  • .mylock
  • .newware
  • .NET1
  • .NZ
  • .perfection
  • .Readinstruction
  • .ReadInstructions
  • .readinstructions
  • .rs
  • .skynet
  • .stopflies
  • .tyco
  • .tyco
  • .uslockhh
  • .uslockhh
  • .zoomzoom
  • n.exe
  • nt_lock20
  • .networkmaze
  • .VinDizelPux
  • .EG
  • .support
  • .deadfiles
  • .readtheinstructions
  • .lr
  • .divsouth
  • .lockfilesCO
  • .lockfilesKR
  • .EMPg296LCK

The following is a list of known MedusaLocker's ransom notes:

  • !!!HOW_TO_DECRYPT!!!
  • how_to_ recover_data.html
  • how_to_recover_data.html.marlock01
  • How_to_recovery.txt
  • instructions.html
  • readinstructions.html
  • readme_to_recover_files
  • recovery_instruction.html
  • recovery_instructions.html

What is the Status of Coverage?

FortiGuard Labs provides the following AV coverage against known samples of MedusaLocker ransomware:





















#StopRansomware: MedusaLocker (CISA)

Alert (AA22-181A) #StopRansomware: MedusaLocker (CISA)


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.