Why credential theft still works in Active Directory

Hello,

In our last issue of Authentication Insights, we explored the gap between authentication policy and implementation. Today, let's look at one of the main reasons why that's the case.

Even in organizations that have deployed MFA widely, credential theft remains one of the most reliable ways attackers move through Active Directory environments.

When people think about credential theft, they often picture phishing attacks stealing usernames and passwords.

But modern Active Directory attacks usually focus on something different: authentication artifacts such as NTLM password hashes, Kerberos tickets, cached credentials, and service account secrets. Once attackers obtain these, they often don't need the password at all.

The challenge isn't just protecting credentials. It's controlling where they appear and how they can be reused.

MFA is extremely effective at protecting interactive sign-ins. But many credential theft techniques operate after authentication has already taken place.

• Pass-the-Hash reuses an NTLM hash.

• Pass-the-Ticket reuses a Kerberos ticket.

In each case, attackers aren't logging in the way a normal user would: they're replaying authentication artifacts the domain already trusts. Once one credential is compromised, the rest of the environment is within reach through lateral movement.

Many of those movements use trusted authentication mechanisms, not obvious brute-force attacks.

Preventing credential theft in Active Directory isn't just about stronger passwords or more MFA. It's about limiting where authentication material appears and how it can be reused.

The techniques we talk about above (Pass-the-Hash, Pass-the-Ticket, credential reuse via stolen service account secrets) all depend on one important factor: authentication material being available somewhere an attacker can reach it. That's the problem to solve for.

Modern AD hardening guidance addresses this from several angles:

• Limiting privileged logons reduces the number of systems that hold high-value credential material in memory at any given time.

• Applying MFA broadly still matters. It raises the cost of initial compromise, and applying it at access points beyond the initial login can help prevent privilege escalation from a standard account.

• Separating administrative accounts limits the blast radius if one credential is compromised.

• Restricting NTLM usage removes one of the most commonly abused authentication protocols.

• Implementing context-based access controls (device, IP address, timeframe) can work behind the scenes for users to stop suspicious activity.

• Controlling lateral authentication paths limits how far an attacker can move even after obtaining a credential.

None of these eliminate the risk entirely. But together, they reduce the attack surface that credential theft depends on.

Next issue, we'll look at authentication attack paths: how attackers actually move through Active Directory once they have a credential.

Thinking about how to reduce credential exposure? These reads can help:

• How Windows Hello for Business MFA works

• Containing the threat of privilege abuse and escalation

• Identity security: Overcoming Active Directory's pain points

Until next time,

The Authentication Insights Team