The menace actors behind the zero-day exploitation of a recently-patched safety vulnerability in Microsoft Home windows have been discovered to ship two new backdoors referred to as SilentPrism and DarkWisp.
The exercise has been attributed to a suspected Russian hacking group referred to as Water Gamayun, which is also referred to as EncryptHub and LARVA-208.
“The menace actor deploys payloads primarily by way of malicious provisioning packages, signed .msi recordsdata, and Home windows MSC recordsdata, utilizing strategies just like the IntelliJ runnerw.exe for command execution,” Pattern Micro researchers Aliakbar Zahravi and Ahmed Mohamed Ibrahim mentioned in a follow-up evaluation printed final week.
Water Gamayun has been linked to the lively exploitation of CVE-2025-26633 (aka MSC EvilTwin), a vulnerability within the Microsoft Administration Console (MMC) framework, to execute malware by way of a rogue Microsoft Console (.msc) file.
The assault chains contain using provisioning packages (.ppkg), signed Microsoft Home windows Installer recordsdata (.msi), and .msc recordsdata to ship info stealers and backdoors which are able to persistence and information theft.
EncryptHub gained consideration in the direction of the tip of June 2024, after having used a GitHub repository named “encrypthub” to push varied sorts of malware households, together with stealers, miners, and ransomware, through a pretend WinRAR web site. The menace actors have since transitioned to their infrastructure for each staging and command-and-control (C&C) functions.
The .msi installers used within the assaults masquerade as legit messaging and assembly software program reminiscent of DingTalk, QQTalk, and VooV Assembly. They’re designed to execute a PowerShell downloader, which is then used to fetch and run the next-stage payload on a compromised host.
One such malware is a PowerShell implant dubbed SilentPrism that may arrange persistence, execute a number of shell instructions concurrently, and keep distant management, whereas additionally incorporating anti-analysis strategies to evade detection. One other PowerShell backdoor of be aware is DarkWisp, which allows system reconnaissance, exfiltration of delicate information, and persistence.
“As soon as the malware exfiltrates reconnaissance and system info to the C&C server, it enters a steady loop ready for instructions,” the researchers mentioned. “The malware accepts instructions by means of a TCP connection on port 8080, the place instructions arrive within the format COMMAND|
“The principle communication loop ensures steady interplay with the server, dealing with instructions, sustaining connectivity, and securely transmitting outcomes.”
The third payload dropped within the assaults is the MSC EvilTwin loader that weaponizes CVE-2025-26633 to execute a malicious .msc file, in the end resulting in the deployment of the Rhadamanthys Stealer. The loader can be designed to carry out a cleanup of the system to keep away from leaving a forensic path.
Rhadamanthys is way from the one stealer in Water Gamayun’s arsenal, for it has been noticed delivering one other commodity stealer referred to as StealC, in addition to three customized PowerShell variants known as EncryptHub Stealer variant A, variant B, and variant C.
The bespoke stealer is fully-featured malware that may gather intensive system info, together with particulars about antivirus software program, put in software program, community adapters, and working purposes. It additionally extracts Wi-Fi passwords, Home windows product keys, clipboard historical past, browser credentials, and session information from varied apps associated to messaging, VPN, FTP, and password administration.
Moreover, it particularly singles out recordsdata matching sure key phrases and extensions, indicating a give attention to gathering restoration phrases related to cryptocurrency wallets.
“These variants exhibit related functionalities and capabilities, with solely minor modifications distinguishing them,” the researchers famous. “All EncryptHub variants coated on this analysis are modified variations of the open-source Kematian Stealer.”
One iteration of EncryptHub Stealer is noteworthy for using a brand new living-off-the-land binary (LOLBin) method by which the IntelliJ course of launcher “runnerw.exe” is used to proxy the execution of a distant PowerShell script on an contaminated system.
The stealer artifacts, distributed by means of malicious MSI packages or binary malware droppers, have additionally been discovered to propagate different malware households like Lumma Stealer, Amadey, and clippers.
Additional evaluation of the menace actor’s C&C infrastructure (“82.115.223[.]182”) has revealed using different PowerShell scripts to obtain and execute AnyDesk software program for distant entry and the power of the operators to ship Base64-encoded distant instructions to the sufferer machine.
“Water Gamayun’s use of varied supply strategies and strategies in its marketing campaign, reminiscent of provisioning malicious payloads by means of signed Microsoft Installer recordsdata and leveraging LOLBins, highlights their adaptability in compromising victims’ programs and information,” Pattern Micro mentioned.
“Their intricately designed payloads and C&C infrastructure allow the menace actor to take care of persistence, dynamically management contaminated programs, and obfuscate their actions.”
