How can security teams detect modified alarm settings?

What modified alarm settings actually look like in monitoring data

Modified alarm settings usually show up as configuration drift, not as a single obvious event. Look for edits to thresholds, routing, disablement, suppression windows, notification targets, and escalation logic. A change can be malicious even when the alarm system still appears “healthy,” because the attacker’s goal is often to reduce visibility rather than shut monitoring off completely.

Pay attention to changes that alter the meaning of the alert stream. If alarms begin firing less often, stop firing for one class of event, or route to a different team or mailbox, the configuration itself may be the compromise. In practice, the most useful detection is often a comparison between the current alarm state and the known-good baseline for the same environment.

For environments that use central admin consoles, treat alarm policy edits as high-value administrative actions. A small number of edits can affect many downstream systems at once, so one setting change may create broad blind spots. That is why the best detections focus on the control plane, not just on whether an individual endpoint or application still emits alerts.

Which changes deserve immediate attention

Not every alarm edit is suspicious, but some patterns are materially higher risk. Edits made outside an approved change window, changes made by unusual administrators, and repeated suppression of the same alert family should be treated as strong signals. The same applies when an alarm is disabled briefly and then restored, because short suppressions are a common way to hide follow-on activity.

Also watch for changes that are technically “normal” but operationally abnormal, such as lowering thresholds so far that useful alerts disappear or redirecting escalation to an unused queue. If the monitoring system has audit logs, compare the timing of the edit with authentication events, permission changes, and any later gaps in alert delivery. That correlation often shows whether the edit was part of broader compromise rather than routine tuning.

Where possible, preserve the previous version of each policy so you can compare old and new settings side by side. Version history is especially valuable when the visible effect is subtle, because attackers frequently change just one condition or suppression rule and leave the rest intact.

How to prove the setting change mattered

The key question is not only whether a setting changed, but whether that change affected detection. Confirm whether alerts stopped arriving, were delayed, were rerouted, or were reduced to an unexpectedly low volume after the edit. If the system supports test events, replay a harmless test signal to verify that the alert still lands in the expected place with the expected priority.

Correlate the configuration change with the surrounding security timeline. If the alarm edit happened shortly before credential use, privilege escalation, data staging, or unusual process activity, treat the edit as part of the attack chain until proven otherwise. This is where NIST Cybersecurity Framework 2.0 is useful, because the Detect and Respond functions help teams connect control failures to operational response.

For teams that manage multiple platforms, the same logic should be applied to all monitoring layers, not just the SIEM. Alarm tampering can occur in cloud consoles, SaaS admin tools, endpoint tools, OT monitoring systems, and email-based alerting. A broad review prevents false confidence when one platform still looks healthy but another has been silently muted.

Practitioner Guidance

What to verify: Confirm who approved the alarm edit, when it occurred, what changed, and whether the resulting alert path still reaches a live responder. If the change cannot be tied to a normal maintenance event, treat it as a security investigation rather than a housekeeping task.

What to prioritise: Start with the most sensitive alarm classes first, especially alarms for authentication abuse, privilege changes, data exfiltration, and policy tampering. Those are the settings attackers most often suppress before attempting deeper actions.

Decision rule: If an alarm change affects alert delivery, routing, or suppression, investigate it as a control compromise even if the underlying system is still operational. If it only adjusts thresholds, verify whether the new threshold removes detection of the exact behaviour you care about.

Practitioner takeaway: The most important judgement is to separate harmless tuning from visibility loss, because a small configuration edit can remove detection long before it creates an obvious outage.

Related resources from NHI Mgmt Group

• Guide: OT Security Guide
• Why are NHIs a critical concern for security teams?
• What steps should security teams take to prevent Shadow AI risks?
• Why is the abuse of NHIs a priority for security teams?
• What is the difference between SAST and DAST for security teams?