Gentlemen Ransomware Emerges with Aggressive EDR Evasion Tactics

Executive Summary

A new Ransomware-as-a-Service (RaaS) group calling itself The Gentlemen has been identified in the wild, employing an aggressive strategy focused on dismantling endpoint security controls. The group's ransomware variant is notable for deploying a suite of Endpoint Detection and Response (EDR) and antivirus (AV) termination tools, dubbed the GentleKiller EDR Framework, as a preliminary step before encryption. This tactic of using multiple EDR killers simultaneously aims to neutralize a broad spectrum of security products, thereby ensuring the ransomware payload can execute unimpeded. This approach represents a direct assault on enterprise defense mechanisms and underscores the importance of robust tamper protection and behavioral monitoring to counter such threats.

Threat Overview

The Gentlemen Ransomware operation distinguishes itself by prioritizing defense evasion. Instead of relying solely on obfuscation or fileless techniques, the threat actors actively attempt to terminate security processes and services. By deploying multiple EDR killer tools at once, they create a race condition against the security software and increase the probability that at least one of the tools will succeed in disabling defenses on the targeted endpoint.

This TTP is a direct implementation of T1562.001 - Disable or Modify Tools. Once the EDR/AV agent is disabled or killed, the ransomware proceeds with its primary objectives: discovering and encrypting files on local and network drives (T1486 - Data Encrypted for Impact). The group has already been linked to successful attacks against several organizations, including Amigest, Burris & MacOmber, PLL, and COFAQ, indicating its effectiveness.

Technical Analysis

The attack chain for The Gentlemen ransomware typically involves the following stages:

1. Initial Access: (Not specified in articles, but common vectors include phishing, exploiting public-facing applications, or using initial access brokers).
2. Defense Evasion: The core of their novel strategy. Upon execution, the initial payload launches the GentleKiller EDR Framework. This framework is not a single tool but a collection of known and custom scripts and binaries designed to target specific security products. It attempts to:
   • Stop security-related services.
   • Kill security agent processes.
   • Unload kernel drivers associated with EDR/AV products.
   • Modify registry keys to disable security features. This multi-tool approach is a brute-force method to overcome endpoint defenses.
3. Impact: Once defenses are confirmed to be disabled, the ransomware payload is executed. It enumerates local drives, connected removable media, and accessible network shares to encrypt files. It then typically drops a ransom note on the desktop and in each encrypted directory.

The use of a multi-tool EDR-killing framework is a logical evolution of ransomware tactics. Instead of hoping to evade a specific product, attackers are now attempting to incapacitate the entire class of security software, making detection and response significantly more challenging.

Impact Assessment

The business impact of a successful attack by The Gentlemen ransomware is severe, compounded by its ability to disable security tools. The primary impact is the immediate operational disruption caused by the unavailability of critical data and systems. Because the EDR is disabled, incident responders may lack the necessary telemetry to investigate the breach, determine the root cause, and understand the full scope of the compromise. This blindness extends the recovery time and increases the cost of remediation. The reputational damage and potential for data exfiltration (double extortion) further amplify the financial and operational consequences.

IOCs — Directly from Articles

No specific file hashes, IP addresses, or domains were provided in the source articles.

Cyber Observables — Hunting Hints

Security teams may want to hunt for the following patterns which could indicate related activity:

Detection & Response

Detection:

• Tamper Protection: The most critical defense is enabling and hardening EDR/AV tamper protection features. Ensure that these settings are configured to their highest level and generate high-severity alerts upon any attempt to stop services, kill processes, or modify agent files.
• Behavioral Monitoring: Use a security solution that focuses on behavioral detection rather than just static signatures. An alert should be generated when a process attempts to enumerate and terminate multiple security tools. This is a key capability of Behavior Prevention on Endpoint (M1040).
• Log Auditing: Monitor Windows Event Logs for service stop/delete events (Event ID 7034, 7045) and process termination events related to your security products. D3FEND's Process Analysis (D3-PA) is a relevant defensive technique.

Response:

1. If a tamper alert is received, immediately isolate the affected host from the network to prevent the ransomware from spreading.
2. If possible, trigger a memory dump of the machine to capture the EDR killer tools and the ransomware payload for analysis.
3. Assume that other machines may be compromised and begin a broader threat hunt for similar activity.
4. Engage incident response and ransomware recovery specialists.

Mitigation

Immediate Actions:

• Review Tamper Protection: Immediately audit all EDR/AV agent configurations to ensure tamper protection is enabled and set to its most restrictive level. Test that it effectively prevents service stops and process kills.
• Principle of Least Privilege: Ensure that standard user accounts do not have administrative privileges. Many EDR killer tools require elevated permissions to function effectively. This aligns with M1026 - Privileged Account Management.

Strategic Improvements:

• Application Control: Implement application control policies, such as AppLocker or WDAC, to restrict the execution of unauthorized binaries. This can prevent the EDR killer tools from running in the first place. This is a form of M1038 - Execution Prevention.
• Defense in Depth: Do not rely solely on EDR. Layer defenses with network segmentation, regular backups (stored offline and immutable), and user training to create a more resilient security posture.
• Backup and Recovery: Maintain and regularly test offline and immutable backups. This is the ultimate safety net against a successful ransomware attack.