Security Experts:

Connect with us

Hi, what are you looking for?


Malware & Threats

PyCL Ransomware Test Campaign Spotted in the Wild

A new ransomware family being dropped by the RIG exploit kit (EK) appears to be in the testing phase and could surface as a major threat, security researchers warn.

A new ransomware family being dropped by the RIG exploit kit (EK) appears to be in the testing phase and could surface as a major threat, security researchers warn.

Dubbed PyCL, the ransomware variant was seen being distributed via the EITest compromise chain into the RIG EK, one of the largest malware distributors at the moment. The malware is written in Python, with the script called, which determined BleepingComputer’s Lawrence Abrams to name the threat PyCL.

The ransomware was first dropped by EITest-RIG on Sunday, in a campaign that abused hacked websites to redirect visitors to the EK and attempted to exploit vulnerabilities on their computers for further compromise. However, PyCL was dropped for a single day, and the security researcher sees it as an indicator that this was only a test run.

The new threat is distributed as an NSIS installer that contains a Python package designed to encrypt the user’s files, and a tutorial on how to pay the ransom. Apparently, the malware communicates with the command and control (C&C) server during each stage of the encryption process, to provide debugging/status information to the developer.

David Martínez, one of the researchers who discovered the malware (alongside KafeineMalwareHunterteamBroadAnalysis), found a file called user.txt in the installer and discovered that a string in it is being sent to the C&C during every request. According to Abrams, this suggests the PyCL is part of a Ransomware as a Service (RaaS), where the username is the affiliate identifier.

The ransomware was first observed checking if it has administrative privileges and deleting the shadow volume copies on the computer if it does. Next, the malware sends the victim’s Windows version to the C&C, along with details such as administrative privileges, screen resolution, processor architecture, computer name, username, and the MAC address of the primary network adapter.

PyCL uses a unique AES-256 encryption key for each file, saves the list of files and their decryption keys to a random named file in the CL folder, and encrypts the file using the RSA-2048 public encryption key. 

While most ransomware families replace user’s files with their encrypted counterparts, this piece of malware leaves the original files on the hard disk, meaning that users don’t have to pay the ransom to get them back (this, however, might change in future versions of the malware). Finally, PyCL displays a lock screen that contains a 4-day timer, a Bitcoin address, and the ransom amount.

Related: Sage 2.0 Ransomware Demands $2,000 Ransom

Related: Destructive KillDisk Malware Turns Into Ransomware

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

Click to comment

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

Expert Insights

Related Content

Malware & Threats

Microsoft plans to improve the protection of Office users by blocking XLL add-ins from the internet.


A recently disclosed vBulletin vulnerability, which had a zero-day status for roughly two days last week, was exploited in a hacker attack targeting the...


CISA, NSA, and MS-ISAC issued an alert on the malicious use of RMM software to steal money from bank accounts.


Russia-linked cyberespionage group APT29 has been observed using embassy-themed lures and the GraphicalNeutrino malware in recent attacks.


No one combatting cybercrime knows everything, but everyone in the battle has some intelligence to contribute to the larger knowledge base.

Malware & Threats

Security researchers are warning of a new wave of malicious NPM and PyPI packages designed to steal user information and download additional payloads.


Chinese threat actor DragonSpark has been using the SparkRAT open source backdoor in attacks targeting East Asian organizations.


The changing nature of what we still generally call ransomware will continue through 2023, driven by three primary conditions.