Inside GentleKiller: The EDR-Killer Powering The Gentlemen

Pierluigi Paganini
June 20, 2026

The Gentlemen equips affiliates with a centralized EDR-killer suite, rapidly weaponizing BYOVD exploits to disable security tools before ransomware attacks.

ESET published a detailed breakdown of The Gentlemen‘s technical infrastructure on June 18, the result of months of incident-level investigation corroborated by the group’s own internal data leak from May 2026. Since emerging in late 2025, The Gentlemen has claimed 504 victims and established itself as one of the five most active ransomware operations in Q1 2026. What sets them apart isn’t the ransomware payload. It’s what they hand to affiliates before the payload ever runs.

Most ransomware-as-a-service operators leave affiliates to find their own tools for disabling endpoint security. The Gentlemen took a different approach.

“Gentlemen demonstrates an interesting approach: operator-managed EDR killers, ready to use by affiliates.” reads the report published by ESET. “While most ransomware gangs continue to delegate EDR killing to affiliates, Gentlemen has chosen to centralize this function by offering affiliates a ready-to-use, standardized EDR-killer suite. This decision makes Gentlemen an attractive operator for affiliates as it materially lowers the entry barrier for them, making their job consequently easier.”

The leaked internal data confirmed what ESET had hypothesized since February 2026: the group’s leader, operating under the handle zeta88, openly discussed maintaining and distributing EDR killer packages to affiliates.

The centerpiece of that suite is GentleKiller, an in-house framework with at least eight distinct variants. Each one impersonates a different legitimate product and abuses a different vulnerable or malicious kernel driver through a technique called Bring Your Own Vulnerable Driver, or BYOVD.

“GentleKiller is by far the most prevalent EDR killer observed in the Gentlemen ecosystem. At the time of writing, we are aware of at least eight distinct variants, each impersonating a different legitimate product and abusing a different vulnerable or malicious driver.” states ESET.

“When abstracting away the impersonation layer and the specific drivers used, the underlying code reveals numerous structural and behavioral commonalities that strongly suggest the use of a shared development template. This template is reused across variants, with only minimal modifications.”

The eight variants target drivers from Kaspersky, FACEIT Anti-Cheat, Valorant, Javelin, Safetica, Zemana, Qihoo 360, IObit, and the PoisonX rootkit. Across all variants, GentleKiller hunts for over 400 processes belonging to 48 distinct security products, including CrowdStrike, SentinelOne, Microsoft Defender, Sophos, Carbon Black, and ESET itself.

The researchers pointed out that the speed of adaptation is the other defining characteristic.

“This design prioritizes ease of deployment and operational flexibility for affiliates, while minimizing development effort for the operators.” continues the reèprt- “It allows the Gentlemen operators to integrate abused drivers into their toolset very soon after an EDR killer PoC is disclosed. This was the case with UnknownKiller and PoisonKiller, which were adopted within a matter of days.”

ESET measured this in days. The UnknownKiller and PoisonKiller proof-of-concepts were both adopted within days of their public release.

Beyond GentleKiller, the suite incorporates three third-party tools. HexKiller, previously associated exclusively with the Warlock ransomware gang, uses a Baidu Antivirus driver and appeared in Gentlemen intrusions staged in the same GentlemenCollection directory as GentleKiller. ThrottleBlood, more commonly seen in MedusaLocker and DragonForce affiliate attacks, uses a TechPowerUp driver. HavocKiller, disclosed publicly by Huntress in March 2026, was already active in Gentlemen intrusions dating back to January 23rd. ESET’s assessment is that all three were acquired externally by the operators and then standardized with the same defense evasion layer applied to GentleKiller: binary protection via Enigma or Themida, filenames mimicking security vendors, fabricated version information, copied digital signatures, and matching icons.

The victimology breaks a pattern that defines most major ransomware operations. Where Qilin, DragonForce, and Akira all show heavy US concentration, often around half their victims, The Gentlemen’s list skews toward Southeast Asia, South America, and Western Europe. The leaked data suggests this isn’t random: the group selects victims primarily based on FortiGate misconfiguration rather than geography, and centrally distributes targets to affiliates. That’s a structured selection process rather than affiliates each picking their own prey.

ESET also found a Rust-based credential stealer called OxideHarvest, also tracked as buildx641, linked to one of the group’s affiliates. It targets Chrome, Edge, Firefox, Brave, Opera, OperaGX, Vivaldi, Waterfox, and a dozen other browsers, using supplied credentials to log into specified hosts, pull browser credentials, and write them to an output file. Unlike GentleKiller, which shows clear evidence of in-house development, OxideHarvest is attributed to an affiliate named quant rather than the core operators.

Brian Krebs published evidence on June 10 of the true identity of hastalamuerte, the group’s founder, identified as 36-year-old Russian national Alexander Andreevich Yapaev, a former affiliate of Qilin, Embargo, LockBit, Medusa, and BlackLock.

“The breach tracking service Constella Intelligence reports that Hastalamuerte’s Telegram ID is connected to another username — “bu4vs” — and to the Russian phone number 79127650004.” wrote Krebs. “Pivoting on this phone number in Constella fetches multiple records from hacked Russian government databases showing it is assigned to one Alexander Andreevich Yapaev, a 36-year-old from Izhevsk.”

According to the report, The Gentlemen rapidly weaponizes newly disclosed BYOVD proof-of-concepts, often incorporating vulnerable driver exploits into operations within days of public release.

For defenders, the ESET report’s practical implication is this: GentleKiller’s process targeting list is now public, which means defenders can use it to design monitoring and detection strategies that remain effective even against variants that haven’t been built yet.

“Gentlemen demonstrates an interesting approach: operator-managed EDR killers, ready to use by affiliates. While most ransomware gangs continue to delegate EDR killing to affiliates, Gentlemen has chosen to centralize this function by offering affiliates a ready-to-use, standardized EDR-killer suite.” concludes the report. “This decision makes Gentlemen an attractive operator for affiliates as it materially lowers the entry barrier for them, making their job consequently easier.”

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