Gentlemen Ransomware Deploys Modular EDR-Killing Framework with Cross-Gang Tools The Gentlemen ransomware operation has adopted a sophisticated, modular approach to evading endpoint detection and response (EDR) systems, leveraging tools sourced from multiple criminal groups. According to an analysis by cybersecurity firm ESET, the gang’s arsenal includes GentleKiller a custom-built EDR killer with at least eight variants alongside borrowed tools like HexKiller, ThrottleBlood, and HavocKiller, previously used by other ransomware gangs. GentleKiller employs the bring your own vulnerable driver (BYOVD) technique, using eight distinct vulnerable drivers to gain kernel-level privileges. Its target list spans over 400 processes across 48 security vendors, including Microsoft, CrowdStrike, SentinelOne, and ESET itself. The tool impersonates legitimate software, such as Kaspersky and Valorant, and uses commercial packers like Enigma and Themida for obfuscation. The modular design allows affiliates to swap drivers without rewriting core code, complicating defenses static blocklists may catch one variant while leaving others operational. Beyond GentleKiller, the gang incorporates tools from rival groups, including HexKiller (linked to Warlock), ThrottleBlood (used by MesudaLocker and DragonForce), and HavocKiller (seen in multiple ransomware campaigns). This tool-sharing creates redundancy, attribution challenges, and tactical flexibility for affiliates. ESET also identified OxideHarvest, a Rust-based credential stealer likely developed externally. The gang’s targeting strategy includes exploiting FortiGate configurations, as seen in the compromise of Romanian energy provider Oltenia. A SystemBC proxy botnet, comprising over 1,570 corporate hosts, provides persistent access for EDR-killer-assisted attacks. The overlap between SystemBC detections and Gentlemen ransomware activity suggests energy-sector defenders should treat such infections as potential indicators of compromise. ESET’s findings highlight the gang’s operational persistence, with 478 victims documented before the modular framework was fully analyzed. The interchangeable nature of the tools combined with stolen digital signatures and rapid driver swaps makes detection and attribution increasingly difficult. Defenders are advised to audit driver blocklists against all eight GentleKiller variants, flag multi-gang EDR killer signatures in incidents, and harden FortiGate configurations to reduce exposure.