NHI Threats & Mitigation Part 3: Idle Secrets and NHIs

Non-Human Identities (NHIs) operate in the background, they move data, enable automation, and access sensitive resources throughout different services and highly distributed environments. Yet, many NHIs become idle and remain unmonitored, making them ideal targets for compromise. A stolen API key or orphaned service account can persist undetected for a long period of time, granting long-term access to the organization’s most critical systems. Meanwhile, idle secrets – never rotated, never revoked – become convenient entry points for threat actors.

In this third installment of Entro Labs NHI Threats & Mitigation, we’ll cover:

• The risks of idle secrets: how lack of visibility and forgotten credentials enables silent & persistent breaches.
• Mitigation strategies: how security teams can better govern and manage the NHI lifecycle.

If NHIs aren’t actively monitored, rotated, or revoked, they become a ticking time bomb – one attacker will inevitably explo(de)it.

NHIs: Unseen, Unused, and Wide Open for Exploit

NHIs don’t operate like human entities. They don’t log in at set hours, don’t request access through traditional workflows, and rarely trigger security alerts. Adding to the risk, many NHIs continue to hold permissions long after they’re actively in use. According to the 2025 Entro Labs Cybersecurity report, 40% of identified secrets are idle, meaning the programmatic access keys of NHIs are left valid and no longer used. Static, forgotten secrets create a security blind spot, letting bad actors exploit stale valid credentials without triggering alarms.

The problem worsens because security teams lack visibility into how NHIs interact with critical systems within the organization. Without proper behavioral monitoring, abnormal activities – such as an NHI suddenly accessing a new environment or pulling large volumes of keys from a vault – go unnoticed. Meanwhile, unrotated secrets remain valid indefinitely, allowing attackers to establish persistent access without being detected (for months and sometimes even years).

When NHIs operate ungoverned and secrets remain static, organizations are left with a growing, invisible attack surface – one that attackers are in fact able to see and more than ready to target.

Idle Secrets Risks: Forgotten, But Not Gone

As organizations scale, secrets proliferate, API keys, access tokens, and service accounts spread across multi-cloud environments, microservices, DevOps workflows, and more. Security teams struggle to track them, leading to a buildup of forgotten, stale, and unmonitored NHI credentials.

Why Do Secrets Become Idle?

• Former employees: offboarding humans often leaves active credentials with no ownership.
• R&D sprawl: Dev teams create NHIs for testing and automation, but cleanup is rare.
• Poor hygiene: secrets that lack expiration policies and stay valid indefinitely.

Once forgotten, idle secrets don’t disappear – they persist.

The Lasting Impact of Lasting Secrets

Stale or idle secrets, especially those tied to authentication, can have severe and long-term security consequences:

• Persistent unauthorized access: attackers who obtain idle secrets maintain prolonged access to critical systems. Since these credentials remain valid, they can move freely across environments.
• Undetected breaches: without expiration or rotation, compromised secrets can go unnoticed for months or years, allowing attackers to escalate privileges, move laterally, and exfiltrate sensitive data over time.
• Data theft and integrity loss: unauthorized access to idle programmatic credentials puts customer data, financial records, and intellectual property at risk. Attackers can steal, alter, or destroy critical business information.
• Operational disruptions: compromised secrets enable attackers to manipulate services, disable security controls, or disrupt workflows, leading to downtime, failed deployments, and loss of business continuity.

The longer idle secrets remain “enabled”, the greater the risk of financial losses, compliance violations, and reputational damage.

Mitigation Strategies: Eliminating Idle Secrets Pre-Exploit

To prevent long-term exposure and unauthorized access, security teams must adopt and enforce strict lifecycle management for NHIs and their secrets.

Automate Rotation & Expiry

• Enforce automated secret rotation for API keys, tokens, and certificates. This minimizes human error and ensures secrets are consistently updated.
• Set rotation schedules based on sensitivity, high-impact credentials should rotate more frequently than lower-risk secrets.
• Use secrets security platforms that integrate with your infrastructure to rotate credentials seamlessly without breaking workflows.

Entro’s platform detects and flags idle NHI and secrets that have not been rotated for extended periods – in this case, a GitHub Private Access Token hasn’t been rotated for over four months. 

Set Hard Expiration Dates for Secrets

• Apply mandatory expiration policies to all secrets, ensuring they become invalid after a predefined period.
• Automate expiration alerts to enforce timely rotation and prevent idle secrets from lingering.
• Enforce shorter expiration timelines for Super NHIs, preventing indefinite access to critical systems.

Audit & Track Secrets Continuously

• Conduct routine audits to identify unrotated or expired secrets before they become security liabilities.
• Maintain an inventory of all secrets with metadata, including creation time, last usage, and expiration.
• Regularly review NHI tokens, API keys, and service accounts to remove unnecessary access and limit privilege creep.

Entro automatically flags secrets and tokens that haven’t been used for at least 30 days – helping security teams identify and eliminate stale credentials before they become attack vectors. The idle threshold is fully configurable, allowing organizations to align detection policies with their security posture and compliance requirements.

Enforce Secret Rotation During Offboarding

• Integrate secret revocation and rotation into the employee offboarding process to prevent lingering access.
• Automate workflows that disable or rotate credentials tied to offboarded employees.
• Ensure that NHIs tied to former employees are reassessed, and any unnecessary accounts are decommissioned.

By enforcing automated secret lifecycle management, organizations can eliminate idle credentials before attackers have the chance to exploit them.

Entro automatically detects and flags active credentials tied to former employees, highlighting potential security gaps in the offboarding process. By identifying lingering service accounts and programmatic keys still in use, security teams can revoke or rotate credentials before they become entry points for attackers. 

Stay Ahead of Non-Human Identities Threats

Idle secrets and unmonitored NHIs are silent security gaps that attackers exploit for persistent access. Without strict governance, these forgotten credentials become hidden entry points, enabling breaches that go undetected for months. To stay ahead, modern organizations need automated enforcement, from real-time monitoring to secret expiration and live alerts, to eliminate these blind spots before they’re exploited.

Entro’s platform gives security teams full visibility and control over NHIs across infrastructures and clouds, reducing risk and preventing credential misuse. If you want to learn more about how Entro helps dozens of CISOs and security teams mitigate NHI threats, detect leaked secrets in real-time, and secure the machine identity attack surface.