What are the signs that an Active Directory environment is not protected against relay and Kerberos abuse?

Common warning signs include relying only on patching without validation, depending on manual testing, and failing to check whether certificate services and Kerberos behavior still allow the exploit chain. If controls have never been exercised against realistic attack paths, teams may assume they are safe while critical gaps remain. Repeated authentication attempts or unexpected machine-account activity can also signal exposure.

How to read the warning signs in a vulnerable AD environment

When active directory is exposed to relay and Kerberos abuse, the warning signs are usually procedural before they are obvious in logs. A team may rely on patching alone, assume certificate services are safe because no exploit has been observed, or accept manual spot checks as proof of control. That confidence gap is often the first sign that the environment has not been validated against a realistic attack path.

A stronger indicator is when security testing never exercises the full chain from authentication through certificate issuance and onward to privilege escalation. If the environment has not been checked against known relay conditions, Kerberos delegation behavior, or AD CS abuse paths, then the absence of incidents says little. The control may exist on paper while the exploitable path remains open.

Operationally, this also shows up as weak visibility into machine-account behavior and authentication anomalies. Repeated failed logons, unusual service-ticket activity, or unexpected account usage patterns can indicate that someone is probing for relay success, abusing trust relationships, or testing whether Kerberos tickets can be coerced into something useful.

Which control gaps matter most?

The most important gaps are not usually a single missing patch, but the absence of layered validation. If certificate services, delegation settings, and authentication pathways are not reviewed together, defenders can miss the combination that makes relay or Kerberos abuse work. This is especially true in hybrid or segmented environments where one weak trust edge can still reach a high-value account or service.

Another common signal is incomplete ownership. When no one can clearly state which team owns certificate templates, delegation configuration, machine-account hygiene, and attack-path testing, the environment tends to drift. That drift creates the conditions for stale settings, overbroad trust, and security assumptions that are never rechecked after change.

Finally, if controls are measured by configuration intent rather than observed behavior, the environment is probably underprotected. A hardened setting that has not been tested against relay, coercion, or Kerberos abuse may not actually withstand those techniques in practice.

What should practitioners look for first?

Start by validating whether the environment has been tested against the attack path, not just against individual settings. If the answer is “we patched it” or “we reviewed the GPO,” that is not enough. You want evidence that certificate services, Kerberos behavior, and machine-account activity have been exercised in a way that reflects realistic abuse, including cases where an attacker already has foothold-level access.

Next, compare what is monitored with what can actually be abused. Unexpected authentication attempts, unusual service account use, and odd machine-account activity deserve attention because they often surface before a full compromise is visible. If those signals are not being correlated, the environment may be blind to a low-noise attack path.

Two NHIMG resources are useful here: the Active Directory and Entra ID Hardening Guide for the trust relationships that typically need review, and the NHI Lifecycle Management Guide for the ownership, visibility, and rotation discipline that keeps machine-oriented access from going stale.

Risk and Threat Considerations

Relay and Kerberos abuse are dangerous because they often exploit trust that defenders treat as routine. If certificate services, delegation, or machine authentication are overtrusted, an attacker can turn a small foothold into broader access without needing loud exploitation. That makes the environment look stable right up until privilege is already expanding.

Failure mechanism: The exploit path succeeds when authentication, certificate issuance, or ticket handling can be manipulated faster than the controls that are supposed to detect or constrain it. Weak validation, stale configuration, and unreviewed trust relationships make that path easier to use and harder to notice.

Impact: The result can be credential abuse, unauthorized access, lateral movement, and escalation toward high-value accounts or services. In practical terms, the warning sign is not only a missed alert, it is an environment where the attack chain still works despite appearing hardened.

Standards & Framework Alignment

This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.

MITRE ATT&CK addresses the attack and risk surface, while NIST SP 800-53 Rev 5 sets the governance and control requirements practitioners need to meet.

Framework	Control / Reference	Relevance
NIST SP 800-53 Rev 5	IA-5 — Authenticator Management	Credential and machine-account hygiene are central to relay and Kerberos abuse detection.
	IA-9 — Service Identification and Authentication	AD relay and Kerberos abuse often hinges on service-to-service authentication and trust.
	AC-6 — Least Privilege	Overbroad permissions and delegated access amplify the impact of Kerberos and relay abuse.
Recommendation — Review authenticator lifecycle controls and rotate or retire credentials that could support relay abuse. Validate service authentication paths and restrict service-to-service trust that enables relay abuse. Reduce privileges on accounts and services that could be leveraged for escalation.
MITRE ATT&CK	T1550 — Use Alternative Authentication Material	Relay and Kerberos abuse commonly leverage stolen or relayed authentication material.
	T1021.002 — SMB/Windows Admin Shares	Relay-based paths often lead into Windows lateral movement and remote execution behavior.
Recommendation — Map observed activity to authentication-material abuse and hunt for alternate-authentication use. Correlate suspicious Windows remote-access activity with possible relay-enabled lateral movement.

Practitioner Guidance

What to verify: Confirm that relay and Kerberos abuse paths have been tested end to end, not inferred from patch status or configuration review alone. If certificate services, delegation, or machine-account behavior were never exercised in a realistic scenario, treat the control state as unproven.

What to measure: Track repeated authentication failures, unexpected machine-account activity, and any signal that suggests coercion or ticket abuse is being probed. The useful metric is not just alert volume, but whether those events are correlated into an attack-path view that someone actually reviews.

Practitioner takeaway: In this class of environment, the safest assumption is that “not yet observed” is not the same as “not exploitable”; only validated attack-path testing proves the control chain is working.