Securing Windows: How to Harden NTLM Authentication and Protect Your Credentials in 2025

If you’ve ever wondered whether the relics of IT’s past can come back to haunt you, look no further than NTLM authentication—a sort of ancient curse that’s less Indiana Jones and more Office Space. Windows still ships with this timeworn authentication protocol enabled by default. While it was a star performer in a bygone era (mid-90s cool points?), today it acts more like the unwitting extra in a security horror show, primed to leak your credentials quicker than you can say “I thought we patched that!”

Understanding the NTLM Credential Threat Landscape​

NTLM, or NT LAN Manager, is the authentication protocol equivalent of your granddad’s station wagon: it gets the job done, but you’re one fender-bender away from a trip to the scrapyard. The NTLM system takes your actual password, processes it into a “hash”—sort of like putting your lunch in a blender—and then uses that hash to verify your identity. The goal, once upon a time, was to keep your password off the network. But here’s the catch: if someone gets onto your PC, the hash is exposed anyway, and with enough time (or a rainbow table), attackers can reverse engineer your code like a teenager guessing the Netflix password.
What’s truly alarming is the continued relevance of NTLM even in 2025. Security researcher Check Point recently took to the blogosphere to highlight CVE-2025-24054—a gaping hole through which NTLM hashes are leaking faster than trade secrets at a high school reunion. This particular exploit, it turns out, is already winging its way through Poland and Romania’s governmental and enterprise systems like a zero-day poltergeist. Attackers, armed with “man-in-the-middle” attacks, pass-the-hash (PtH), rainbow table, and relay techniques, are specifically targeting admins and privileged users—aka the people you least want to see compromised.

A Dose of IT Reality​

Aside from the immediate “get patched!” energy here, this threat highlights the enduring weirdness of enterprise IT: protocols older than TikTok users still sit at the heart of your security model. The notion that NTLM is still around, enabled by default, should give every IT professional pause—especially if you assumed Windows security meant more than “just trust us and update sometimes.”

Where the Rubber Meets the Home User​

Critically, NTLM threats are not the sole concern of stock photo-friendly corporate settings. Home users, often blissfully unaware of the dark arts of credential theft, are at risk too. All it takes is the digital equivalent of shaking hands with the wrong file—or, say, an enticing “free PDF to DOC converter”—and your Windows login hashes are off souvenir-shopping in a hacker’s database.
So, what’s a user to do? Microsoft did, to its credit, roll out a patch for CVE-2025-24054. But security never ends at a patch; it’s about defense in depth. If you’re ready to go beyond “set it and forget it,” there are several configuration changes that slam the door on NTLM-based attacks with all the subtlety of IT on a Friday afternoon.

How to Harden Your NTLM Credentials: The Practical Steps​

Let’s break down the four big moves you can make, with a little commentary along the way—because “just tweak this registry key” never tells the whole story.

1. Disable NTLM Authentication over SMB Using PowerShell​

First up, disabling NTLM over the Server Message Block (SMB). It’s as straightforward as opening PowerShell (as administrator, naturally—right-click, “Run as administrator,” the sacred incantation of modern IT) and entering:
Set-SMBClientConfiguration -BlockNTLM $true
This single setting tells your Windows device to block NTLM authentication on SMB connections—the digital equivalent of shutting the drawbridge on a medieval castle. Most modern devices won’t even blink, but if you’re using prehistoric networked hardware (the printer in the basement labeled “Do not touch—works sometimes”), you might ruffle feathers. Not to worry: you can reverse it with
Set-SMBClientConfiguration -BlockNTLM $false
And in case you’re wondering, yes—this highlights how much of your network security is maintained by things you literally can’t see or touch. If your organization’s SMB traffic is still relying on NTLM, it’s time for a heart-to-heart with your network inventory.

Commentary: Breaking Habits (and Legacy Devices)​

Blocking NTLM here is one of those “low regret, high gain” moves for most users, but real-world IT is never ideal. Whether it’s that one dusty NAS box or the mythic printer that “just needs NTLM,” sometimes disabling legacy support is the spark for discovering all the dependent artifacts you forgot you owned. Still, the reduction in attack surface is significant—if attackers can’t relay NTLM hashes over SMB, you’re largely immune to the splashiest types of credential theft.

2. Disable NTLMv1 and Enforce NTLMv2 via Registry Tweaks​

Kerberos is the reigning authentication champion these days, but you’ll often find NTLM still hanging around—especially on larger networks, or anywhere a really stubborn third-party app sits and sulks. While there’s no need to kill off NTLM entirely, disabling its oldest and weakest flavors is a gift to your security posture.
In the Registry Editor (after backing up, for the love of uptime), trek to:
Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
The pivotal value here is “LmCompatibilityLevel.” By default, it might not even be present (that’s okay, just create it). Changing its setting to “3”, “4”, or “5” forces NTLMv2, leaving NTLMv1 buried in the sands alongside floppy disks and Netscape Navigator.
Suitably emboldened, move next to:
Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters
Here, seek out “RequireSecuritySignature” or “EnableSecuritySignature.” Ensure its value is “1”—this means all your SMB connections will require actual security signing, which is IT-speak for making sure your device isn't yelling secrets in public.

Commentary: NTLM Versions—Choose Your Fighter​

Why is “v2” so much better than “v1”? NTLMv2 incorporates transaction-based encryption and mutual authentication, which is to say it’s actually trying to keep up with the times. NTLMv1, meanwhile, is so outdated you wouldn’t trust it to guard your leftovers, let alone your credentials.
Messing with the registry is always a bit of a high-wire act, though. For veteran admins, it’s old hat; for everyday users, it’s like defusing a bomb with Google and prayer beads. Fortunately, these two changes are safe as long as you backup and don’t improvise. And if your networked devices freak out after these changes? Congratulations—you’ve just discovered a hidden IT dependency to document (or possibly replace).

3. Lean on Cloud Protection in Windows Security​

Perhaps you, dear reader, are rational and want to avoid the registry entirely (a wise choice for blood pressure management). Good news: Windows Security now includes the “Cloud-delivered protection” option. A few clicks deep (Virus & Threat Protection → Manage Settings → Cloud-delivered protection), this setting arms your device against the shifting sands of phishing, malware, and (you guessed it) credential theft.
This approach is like installing an always-on bodyguard who’s not afraid to shout if you download something sketchy. The cloud-powered threat intelligence updates significantly faster than conventional “definition updates” from the pre-cloud era, catching zero-day attacks that haven’t hit mainstream headlines or Patch Tuesday yet.

Commentary: In Praise of (Selective) Automation​

Cloud-driven defense has come a long way from smugly annoyed “clippy” popups. For once, Microsoft’s bet on letting “AI” watch your back actually feels helpful instead of invasive—provided you’re willing to trust big tech’s definition of “privacy.” Still, this defense is only as strong as its internet connection and your willingness to click “enable.”
For IT professionals: Yes, it’s a little unnerving to cede yet another aspect of protection to the cloud, but when a zero-day drops at 3 a.m., rapid response beats nostalgia every day of the week.

4. The Defensive Arsenal: More Than Just Patches​

Microsoft’s official playbook for NTLM credential defense has grown a bit over the years, deserving more than a brief list tacked on at the end. Here’s a curated toolkit any IT pro (or aspiring security buff) should reach for:

• Endpoint Detection and Response (EDR): Solutions like Microsoft Defender don’t just look for known threats; they sniff out suspicious behavior, triaging attacks before they become catastrophic.
• User Account Control and Least Privilege: Give your users the “keys to the kitchen,” not the “keys to the kingdom.” Admin rights shouldn’t be doled out like holiday candy.
• Multi-factor Authentication (MFA): Even if attackers nab the hash, they’ll have to solve another puzzle—perhaps your phone, your face, or some obscure fact about your first pet.
• Disabling Legacy Protocols: If you’re not using something, turn it off. Dead weight invites risk, not productivity.
• Regular Patching: It’s unglamorous but essential—don’t ignore those updates until next quarter.

Commentary: Security Is a Verb​

Each of these steps forms a safety net, not a silver bullet. IT pros know: there’s no single action that eliminates risk, only layers of mitigation. Like onions. Or ogres. When NTLM comes up in your next audit, you’re now equipped to ask: “Why are we still using this?” before some attacker answers that for you.

Real World Implications for IT Professionals​

Let’s get real: In the world of IT, the biggest security gaps are rarely technical—they’re cultural. How long did NTLM linger in your environment out of sheer “don’t rock the boat” inertia? How many legacy apps demand antique protocols? How often do you hear, “Well, it’s always worked before”?
Adopting these hardening steps is as much about shifting mindset as toggling settings. By moving to Kerberos, disabling outdated NTLM, and auditing your authentication landscape, you’re treating your credentials the way you (hopefully) treat your coffee: guarded, fresh, and never left unattended in public spaces.
There’s a hidden risk to all this: complacency. A patch today is only as effective as the awareness and process that made you apply it. As attackers diversify with machine learning and AI, enterprise security must get smarter, not just more complicated.

Hidden Risks You Shouldn’t Ignore​

Even after all your tweaks, the shadow of legacy tech looms long. Here are a few overlooked risks that could bite, even post-patch:

• Third-Party Applications: Many use hardcoded authentication methods; a botched registry tweak could grind an entire workflow to a halt.
• Shadow IT: That “temporary” file server set up five years ago still runs in the closet, blissfully unaware of your security policies.
• Password Reuse: Whether NTLM or Kerberos, if your users are reusing breached credentials, attackers can leapfrog over every barrier you erect.
• Insider Threats: All the protocol hardening in the world won’t protect you from Bob in accounting, who loads malware-laden USBs like they’re fidget spinners.

Commentary: The “Perfect” Security Model Is a Fantasy​

There will always be blind spots. The trick is shrinking them, not pretending they’ve vanished. IT professionals must remain vigilant, skeptical, and—occasionally—willing to annoy end-users with “just one more security setting.”

The Unexpected Upsides: Hidden Strengths​

Not all news is doom and PowerShell. By following these protocols, Windows environments slowly become more manageable. You’ll get cleaner network traffic, reduced support tickets for weird “NTLM credential warnings,” and a team whose only nostalgia comes from retro gaming, not legacy security.
And with every uptick in setting maturity, you free up human capital to focus on real problems: improving uptime, innovating, maybe even sneaking that Friday afternoon off because everything “just works.”

Looking Forward: NTLM’s Last Goodbye?​

Microsoft continues to invest in more modern authentication approaches—from Azure AD to passkeys—hinting that NTLM may finally be headed for retirement. Until then, count on a slow, awkward fade-out, as more organizations get wise to the risks and flush out legacy dependencies.

Final Reflections: IT Wisdom for the Ages​

In the final analysis, zero-day threats like the recent CVE-2025-24054 remind us that offensive security adapts faster than most enterprise change management plans. Defending against NTLM credential theft isn’t about heroics; it’s about blocking old attack lanes, trimming dead branches, and refusing to let the past dictate your future security posture.
So grab your backups, dust off your registry know-how, and keep your PowerShell close. NTLM’s days are numbered—but only if you take the wheel and steer Windows toward safer horizons.
And if anyone asks, “Why bother with all these tweaks? Isn’t NTLM fine?”—just smile, nod, and remind them: in IT security, nostalgia is always overrated.

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Source: Make Tech Easier How to Protect Your Windows NTLM Credentials from Zero Day Threats - Make Tech Easier