Kerberos Archives

Winsage

January 30, 2026

Microsoft to disable NTLM by default in future Windows releases

Microsoft will disable the NTLM authentication protocol by default in the next major Windows Server release and associated Windows client versions. NTLM, introduced in 1993, has been vulnerable to various cyberattacks, including NTLM relay and pass-the-hash attacks. The transition plan includes three phases: enhanced auditing tools in Windows 11 24H2 and Windows Server 2025, new features like IAKerb and a Local Key Distribution Center in late 2026, and eventually disabling network NTLM by default in future releases. NTLM will remain in the operating system but will not be used automatically. Microsoft deprecated NTLM authentication in July 2024 and has encouraged developers to transition to Kerberos or Negotiation authentication.

Winsage

January 27, 2026

Microsoft Phases Out RC4 in Kerberos to Boost Security

Microsoft is phasing out the RC4 encryption method used in Kerberos to address vulnerability CVE‑2026‑20833, which allows attackers to exploit weak encryption for offline cracking of service account passwords. The transition timeline includes an initial phase starting January 13, 2026, with new Kerberos audit events and optional registry controls to identify RC4 usage. In April 2026, domain controllers will default to AES‑SHA1, disabling fallback to RC4. By July 2026, Microsoft will remove Audit mode and enforce Enforcement mode, eliminating RC4 from the Kerberos protocol. Organizations are advised to update Active Directory Domain Controllers, monitor System event logs for new audit events, address KDCSVC events, and activate Enforcement mode to enhance security against RC4-related vulnerabilities.

Winsage

December 19, 2025

Microsoft Phases Out RC4 Encryption by 2026 to Bolster Windows Security

Microsoft has announced the phased discontinuation of the RC4 encryption cipher, with full implementation expected by mid-2026. RC4, created in 1987, has been increasingly recognized as a vulnerability, exploited in various high-profile cyberattacks. Microsoft plans to disable RC4 by default in Windows Kerberos authentication, encouraging organizations to transition to more secure alternatives like AES-256. This decision follows years of warnings from the cybersecurity community and aims to eliminate long-standing cryptographic weaknesses. The transition will require organizations to audit and upgrade their infrastructures, as many legacy applications still depend on RC4. Disabling RC4 is expected to reduce the success rates of attacks exploiting weak encryption. Microsoft has introduced tools to help administrators identify hidden RC4 usage. The change reflects a commitment to zero-trust architectures and aligns with recommendations from organizations like NIST. Experts recommend a multi-step approach for organizations to navigate this transition effectively.

Winsage

December 10, 2025

Beyond RC4 for Windows authentication

Two new PowerShell scripts from the Microsoft Kerberos-Crypto GitHub repository have been introduced to enhance cybersecurity by streamlining the monitoring of Security Event logs on domain controllers. 1. List-AccountKeys.ps1: This script queries the Security Event Log for the Keys field, enumerating the keys associated with accounts in the event logs. It provides details such as the timestamp, account name, account type, and specific account keys. For example, it can show that accounts have access to keys like RC4, AES128-SHA96, AES256-SHA96, and AES128-SHA256. 2. Get-KerbEncryptionUsage.ps1: This script allows users to query events to determine which encryption types Kerberos utilized, revealing requests that employed AES256-SHA96. It also offers filtering options for specific encryption algorithms, such as RC4. Organizations can further enhance their security by using SIEM solutions like Microsoft Sentinel or built-in Windows event forwarding to query these logs.

Winsage

November 12, 2025

Microsoft Fixes 63 Security Flaws, Including a Windows Kernel Zero-Day Under Active Attack

On November 12, 2025, Microsoft released patches for 63 vulnerabilities, including four classified as Critical and 59 as Important. Notably, CVE-2025-62215, a privilege escalation flaw in the Windows Kernel with a CVSS score of 7.0, is actively exploited. This vulnerability allows an authorized attacker to elevate privileges locally through a race condition. Additionally, Microsoft patched two heap-based buffer overflow vulnerabilities (CVE-2025-60724 and CVE-2025-62220) with CVSS scores of 9.8 and 8.8, respectively, which could lead to remote code execution. Another significant vulnerability is CVE-2025-60704, a privilege escalation flaw in Windows Kerberos with a CVSS score of 7.5, enabling attackers to impersonate users and control a domain. Other vendors, including Adobe, Amazon Web Services, and Apple, also released security updates addressing various vulnerabilities.

Winsage

November 12, 2025

Microsoft Releases November 2025 Patch Tuesday Updates

Microsoft has rolled out its November 2025 Patch Tuesday updates for Windows 11, addressing 63 vulnerabilities across various platforms, including Windows, Office, Microsoft Edge, Azure Monitor Agent, Dynamics 365, Hyper-V, and SQL Server. The update includes four critical and 59 important vulnerabilities, with one currently being exploited. Key vulnerabilities fixed include: - CVE-2025-62215: A privilege escalation vulnerability in the Windows Kernel. - CVE-2025-60724: A critical heap-based buffer overflow in the Microsoft Graphics Component (GDI+) enabling remote code execution, rated CVSS 9.8. - CVE-2025-60704: A high-severity vulnerability in Windows Kerberos, rated CVSS 7.5. - CVE-2025-62220: A heap-based buffer overflow in the Windows Subsystem for Linux GUI (WSLg), rated CVSS 8.8. - CVE-2025-60719: An untrusted pointer dereference in the Windows Ancillary Function Driver for WinSock. The update enhances features for Windows 11 versions 25H2 and 24H2, improving Click to Do, File Explorer, Voice Access, and Windows Search for Copilot+ devices. The taskbar has been updated with a new battery icon, and the Start Menu has been redesigned to include a scrollable All section. A preview of the Administrator Protection feature has been introduced to prevent unauthorized changes. Additionally, Microsoft released KB5068781 for Windows 10 Extended Security Updates, fixing an incorrect “end of support” message and addressing the same 63 vulnerabilities. Organizations are advised to conduct thorough testing before deploying the patches and to back up systems to mitigate potential issues.

Winsage

November 12, 2025

Microsoft November 2025 Patch Tuesday fixes 1 zero-day, 63 flaws

Microsoft's November 2025 Patch Tuesday addresses a total of 63 vulnerabilities, including one actively exploited zero-day flaw (CVE-2025-62215) related to Windows Kernel Elevation of Privilege. The updates include four vulnerabilities classified as "Critical," with two for remote code execution, one for elevation of privileges, and one for information disclosure. The breakdown of vulnerabilities is as follows: - 29 Elevation of Privilege Vulnerabilities - 2 Security Feature Bypass Vulnerabilities - 16 Remote Code Execution Vulnerabilities - 11 Information Disclosure Vulnerabilities - 3 Denial of Service Vulnerabilities - 2 Spoofing Vulnerabilities This Patch Tuesday marks the first extended security update (ESU) for Windows 10, and users are encouraged to upgrade to Windows 11 or enroll in the ESU program. Microsoft has also released an out-of-band update to assist with enrollment issues. Other companies, including Adobe, Cisco, and Google, have also issued security updates in November 2025.

Winsage

November 5, 2025

Curly COMrades abuse Hyper-V for covert malware operations in VMs

Bitdefender researchers have identified advanced techniques used by the Curly COMrades threat actor, believed to have Russian backing, to exploit Microsoft’s Hyper-V virtualization platform. This group activates Hyper-V on compromised systems to deploy a lightweight virtual machine (VM) running Alpine Linux, which hosts malware tools CurlyShell and CurlCat. The operation began in early July with commands that activated Hyper-V and prepared the environment for the VM, using deceptive file names to avoid detection. The Alpine Linux VM is customized for each victim, allowing the attackers to maintain a low profile while facilitating reverse shell and proxy activities. The VM routes traffic through the host's network, masking communications as originating from the legitimate host IP. CurlyShell acts as a persistent reverse shell, while CurlCat manages SSH traffic tunneling, utilizing a private key for authentication. The attackers also employ various proxy and tunneling tools and utilize PowerShell scripts for tasks such as injecting Kerberos tickets into LSASS for lateral movement and creating local accounts to ensure ongoing access. Their command and control infrastructure involves compromised servers that relay traffic between infected hosts and the attackers' servers, with measures taken to limit forensic evidence. To detect and mitigate these threats, Bitdefender emphasizes the need for host-based network inspection and hardening, as well as monitoring for abnormal access to the LSASS process and suspicious Kerberos ticket activities. The findings indicate a shift in threat actor tactics towards using virtualization for stealth and persistence, highlighting the need for layered security measures.

Winsage

November 4, 2025

Russian hackers abuse Hyper-V to hide malware in Linux VMs

The Russian hacker group Curly COMrades has been using Microsoft Hyper-V to bypass endpoint detection and response (EDR) solutions by creating a concealed Alpine Linux-based virtual machine for running malware. They have deployed proprietary tools, CurlyShell and CurlCat, within this virtual environment to maintain operational stealth and secure communication. Active since mid-2024, the group targets government and judicial entities in Georgia and energy companies in Moldova. In early July, they gained remote access to two machines, activated Hyper-V, and disabled its management interface to deploy a minimalistic virtual machine that hosted their malware. This tactic allowed them to evade traditional host-based EDR detections. The virtual machine was configured to use the Default Switch network adapter, making malicious traffic appear to originate from the legitimate host's IP address. CurlyShell executes commands and maintains persistence, while CurlCat facilitates covert traffic tunneling. The group also utilized PowerShell scripts for persistence and pivoting to remote systems, including injecting Kerberos tickets into LSASS and creating local accounts via Group Policy. Bitdefender advises organizations to monitor for abnormal Hyper-V activation, LSASS access, and suspicious PowerShell scripts.

Winsage

November 4, 2025

Russian Hackers Abuse Hyper-V to Hide Malware and Evade Endpoint Detection

A Russian-linked hacking group, Curly COMrades, is using Microsoft’s Hyper-V to conceal malware within compromised Windows systems. They install a small Alpine Linux virtual machine (VM) to run custom malware, evading endpoint detection and response (EDR) software since July. The group exploits Hyper-V's native features, enabling it on victim systems while disabling management clients to avoid detection. The VM, named “WSL,” hosts two C++ tools: ‘CurlyShell,’ a reverse shell, and ‘CurlCat,’ a reverse proxy, both designed to maintain persistence and obfuscate their activities. The VM occupies only 120MB of disk space and uses Hyper-V’s Default Switch for network traffic, making malicious communication appear to originate from the legitimate host. Additionally, Curly COMrades employs malicious PowerShell scripts for persistence and lateral movement, including creating local user accounts and using a modified TicketInjector for authentication across networks.