2025 Guide: Protecting Enterprise Data from Windows Authentication Coercion Attacks

Few developments in enterprise cybersecurity have proved as persistent—and as adaptive—as Windows authentication coercion attacks. Despite years of steady security investments by Microsoft and mounting awareness within the IT community, these sophisticated offensive techniques continue to represent a critical risk for corporate Active Directory (AD) environments. As of 2025, authentication coercion attacks not only remain viable, but they have also evolved, incorporating new exploits and tools that allow threat actors with relatively low privileges to escalate all the way to domain dominance within hours. This ongoing threat highlights both gaps in default Windows configurations and the relentless creativity of attackers operating in an age where enterprise perimeter defenses are rapidly vanishing.

Understanding Windows Authentication Coercion​

Authentication coercion is not just another buzzword within cybersecurity circles. It’s a refined family of attack techniques built around a deceptively simple premise: tricking a legitimate Windows computer or service into authenticating to a malicious, attacker-controlled destination. Once this forced authentication occurs, adversaries can relay, intercept, or even replay authentication requests—often with devastating results.
The underlying methods exploit core Windows components, relying on standard Remote Procedure Call (RPC) interfaces such as MS-RPRN, MS-EFSR, MS-DFSNM, and MS-WSP. Each of these is core to everyday Windows operations, and their presence across nearly all domain-joined endpoints and servers makes them uncomfortably universal as attack surfaces.

• MS-RPRN (PrinterBug): Initially intended to streamline printer management, MS-RPRN is present on most versions of Windows except the minimalistic Server Core installations. Attackers exploit this service to coerce a computer into making outbound authentication attempts to a target of their choosing.
• MS-EFSR (PetitPotam): An exploit against the Encrypted File System RPC interface, PetitPotam famously demonstrated that attackers need only induce a system to try EFS operations—something as simple as attempting to create an encrypted file on a network share—to trigger a vulnerable authentication exchange.
• MS-DFSNM (DFS Coercion) & MS-WSP (WSP Coercion): These interfaces facilitate distributed file systems and protocol support, but can also be misused to set up similar coercion relays.

The technical mechanics here often focus on Windows’ use of NTLM (NT LAN Manager) and Kerberos authentication protocols, which—while robust in isolated use—may be subject to relay or impersonation attacks when a trusted machine inadvertently authenticates to an attacker’s controlled system.

Attack Evolution: Tools and Techniques​

Initial discoveries within this attack domain quickly led to practical tools, with open-source projects like ntlmrelayx.py and PetitPotam becoming staples of penetration testing frameworks. As defenders introduced controls such as SMB signing or disabled HTTP-based NTLM authentication mechanisms, attackers responded with more versatile and RPC-aware toolsets.
One such example is the evolving approach to SMB and HTTP relays. With Microsoft's protections increasingly blocking these vectors, researchers integrated RPC server capabilities into attack tools, enabling attackers to sidestep protections intended for the network file and web protocols. The result? Even when standard relay pathways are blocked, coercion via RPC persists.
In 2025, the landscape for attack tools remains vibrant, with automated solutions like NetExec's efsr_spray module making exploitation even more accessible. Instead of waiting for the Encrypted File System Remote (EFSR) service to be manually activated, efsr_spray actively attempts to trigger service activation by creating encrypted files via accessible SMB shares—including printer queue shares. This directly increases the attack surface area and reduces the window for defenders to respond.
It’s important to stress that these offensive techniques aren’t just hypothetical: real-world, high-profile breaches have incorporated authentication coercion as chain links in advanced persistent threat (APT) operations. Incident responders and security consultants alike report that coercion-based relays often serve as critical escalation stages enabling full domain compromise.

Evaluating Microsoft's Countermeasures​

In response to ongoing abuses, Microsoft has steadily ramped up its defense-in-depth strategy:

• Extended Protection for Authentication (EPA): Designed to prevent credential relay attacks by binding authentication to a specific TLS channel, EPA represents a major technical leap. When correctly deployed, it can prevent attackers from successfully relaying authentication requests. However, not all Windows components or legacy applications support it yet.
• LDAP Channel Binding: Channel binding ties LDAP authentication to the ambient TLS context, mitigating Man-in-the-Middle (MitM) attacks. As of Windows Server 2022 23H2, this protection is enabled by default—a significant step forward.
• SMB Signing: By requiring digital signatures on all SMB traffic, Microsoft has made it significantly more difficult to leverage relay attacks that target network shares. Windows 11 24H2 extends this by mandating SMB signing on workstations, tightening the noose around several popular vectors.
• AD CS Web Enrollment Hardening: Windows Server 2025 disables unencrypted Active Directory Certificate Services Web Enrollment APIs, closing another often-abused credential relay avenue.

Despite these advances, Microsoft’s multi-stage upgrade model introduces problematic inconsistencies. Fresh Windows installations enjoy full benefit from default-enabled protections, but systems upgraded from earlier versions typically retain their legacy (and often insecure) configuration. As a result, many enterprise environments are a patchwork of secure and insecure nodes, offering attackers ample opportunity to identify and exploit the weakest link.

The Persistent Threat of Legacy and Configuration Drift​

One of the key takeaways in modern Windows security is that the attack surface is not defined solely by the operating system’s default security posture—configuration drift and legacy practices play a determining role. Organizations often postpone full-scale security reviews after major in-place upgrades, resting on misplaced confidence that “new version” equals “secure.”
Unfortunately, coercion techniques are adept at rooting out such gaps. Because Windows fails open by default when communication with an insecure peer is permitted and required features (such as EPA or signing) are disabled for compatibility, an attacker need not find cutting-edge vulnerabilities. Rather, they simply exploit the reality that many enterprise networks still have “weakest links” by design.
A particularly glaring example is the continued reliance on the WebClient service for HTTP-based coercion attacks. While Microsoft has tightened up some behaviors, techniques leveraging .searchConnector-ms files placed on SMB shares can still activate this service at will—bypassing expected user controls and setting up fresh relays against endpoints that may otherwise seem hardened. WebClient’s ability to be programmatically awakened for external connections thus remains a potent attack vector that is not easily neutered by standard default hardening.

The High Stakes: From Workstation to Full Domain Compromise​

Perhaps the most concerning aspect of authentication coercion is its potential for privilege escalation. Attackers don’t need an initial foothold with elevated rights; rather, these techniques let adversaries exploit machine accounts, not just user credentials.
Windows computer accounts, especially those of servers and domain controllers, possess permissions that are rarely scrutinized in routine reviews. Through abuses of features like S4U2Self and Resource-Based Constrained Delegation (RBCD), attackers that trick a targeted machine into authenticating to their relay infrastructure can eventually impersonate privileged user accounts. When the final target is a Domain Controller, attackers may gain DCSync privileges, letting them extract the entire domain’s credential store (user password hashes), paving the way for total network compromise.
This high-leverage capability remains one of coercion’s most attractive aspects for both penetration testers and real-world attackers—because a single successful authentication relay can rapidly cascade across the trust relationships and delegation chains that underpin enterprise Windows architecture.

As NTLM Deprecation Nears, Kerberos Relay Becomes Paramount​

Looking forward, Microsoft is working to deprecate NTLM altogether, acknowledging that it has long represented a weak point in the authentication stack. However, as the focus shifts more fully to Kerberos, researchers caution that the underlying relay-and-coercion paradigm will not disappear but merely evolve. Kerberos relay attacks—while more complex—are already demonstrably viable in specific configurations, especially given the prevalence of misconfigured delegation rights.
The transition period is itself a risk window: organizations must not only disable NTLM but must also correctly configure Kerberos delegation and signing requirements across all relevant services. Without coordinated, organization-wide effort, attackers will inevitably discover and exploit inconsistent deployments—jumping from a legacy-enabled NTLM path to a misconfigured Kerberos one, circumventing defenses that are only partially applied.

Challenges Facing Enterprise Defenders​

Defending against Windows authentication coercion is a multifaceted challenge requiring much more than default security measures. Organizations confront a complex mixture of old and new hardware, legacy applications, and unique operational requirements. Even with Microsoft setting more secure defaults, the onus is on enterprise IT teams to ensure that protective settings are actually enforced everywhere.

Key Challenges Include:​

• Configuration Inconsistency: Upgraded devices don’t receive all security defaults; variations in SMB signing, LDAP channel binding, and EPA deployment leave ample room for gaps.
• Service Activation and Exposure: Core services like EFSR, RPRN, or WebClient can be triggered remotely by attackers—even if not actively used by the organization—expanding the attack surface.
• Monitoring and Detection Difficulty: Coercion attacks often leverage legitimate Windows features and network traffic, making them difficult to spot using standard intrusion detection/prevention systems (IDS/IPS).
• Complexity of Hardened Environments: Balancing required legacy software functionality with modern security requirements creates friction; many organizations compromise on security to maintain business operations.

Security Best Practices: Building a Resilient Defense​

For security professionals and enterprise defenders looking to stay ahead of coercion-based attacks, a coordinated, multi-layered approach is essential. The following best practices can help significantly reduce the risk:

1. Systematic Configuration Auditing​

Regularly audit all endpoints and servers, focusing on verifying that key security settings (such as SMB signing, EPA, and LDAP channel binding) are enabled. Use automated vulnerability scanning tools that specifically check for coercion attack vectors.

2. Service Hardening and Reduction​

Disable unneeded Windows services—especially the Print Spooler, WebClient, and EFSR services—on all systems where they are not required. Ensure that only necessary machine accounts have delegation rights and routinely review these permissions for drifting or excessive grants.

3. Network Segmentation and Access Controls​

Segment critical infrastructure (such as Domain Controllers) onto isolated network tiers. Restrict which hosts are permitted to communicate with key services, and enforce firewall rules that block privileged operations from untrusted endpoints.

4. Maximal Use of Signing and Encryption​

Deploy SMB signing enforcement across all endpoints—not merely servers—and require LDAP signing everywhere possible. Prioritize rollout of EPA where it is supported and ensure all software dependencies are compatible.

5. Continuous Monitoring and Threat Intelligence​

Invest in advanced monitoring solutions that can detect anomalous authentication attempts, particularly computer account logins and API usage patterns aligned with known coercion techniques. Leverage commercial or open-source threat intelligence feeds to speed up detection and contextualization of suspicious events.

6. Update and Patch Management​

Stay abreast of the latest security advisories from Microsoft and major security research labs. Rapidly deploy patches for any discovered vulnerabilities affecting RPC interfaces, authentication services, or new variations of coercion attacks.

7. User and Administrator Education​

Empower administrators with up-to-date knowledge of coercion attack vectors and encourage proactivity in disabling unused delegation paths and authentication protocols across the enterprise.

A Critical and Ongoing Risk​

Despite substantial progress from both Microsoft and the wider cybersecurity community, authentication coercion is not a problem with a single, final solution. As long as Windows remains a highly flexible, highly compatible ecosystem—supporting multiple generations of applications, devices, and authentication methods—the temptation and opportunity for attackers to exploit trust relationships will persist.
It’s easy to underestimate the risk, given that many attacks rely on abusing ‘normal’ network operations. Yet, the persistent adaptation of tools like ntlmrelayx.py, real-world efficacy of creative exploits such as PetitPotam, and rising attention from red and blue teams alike underline just how critical this issue remains.
Microsoft’s ongoing hardening of Windows defaults, particularly in the latest Windows Server 2025 and Windows 11 24H2 editions, should be applauded. However, the company’s gradual and compatibility-minded rollout—while necessary to avoid disrupting existing businesses—means defenders can’t afford to be complacent. Legacy configurations, inconsistent application of security requirements, and overlooked service activation pathways will continue to present attackers with openings.

The Bottom Line: Immediate Action Required​

Active Directory remains the digital backbone of most enterprise organizations. Protecting it in the era of authentication coercion requires a blend of technical vigilance, process discipline, and organizational buy-in. Enterprises should treat coercion-based attacks not as an occasional risk, but as a perennial adversary—one that will evolve in lockstep with both Microsoft’s defenses and the growing sophistication of threat actors.

To summarize:​

• Authentication coercion attacks remain a serious and persistent threat in 2025.
• Organizations must adopt a defense-in-depth approach spanning updated configuration, service hardening, network segmentation, and constant vigilance.
• No single patch or update will render environments fully immune; only sustained, systemic effort can minimize exposure.
• Security teams should prioritize closing gaps in legacy deployments and ensure all systems, upgraded or otherwise, enforce modern security requirements.

As the attack landscape continues to evolve, combatting authentication coercion will require both technical acumen and relentless attention to detail. For enterprise defenders, the time for proactive, comprehensive security is not tomorrow—it’s now.

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Source: CybersecurityNews Windows Authentication Coercion Attacks Pose Significant Threats to Enterprise Networks