The client secret protecting your most important integration was generated when the integration was built, and it will still be valid in five years unless somebody chooses to change it. Machine credentials have no expiry pressure, no owner prompting a reset and no user to notice something is wrong. NIST’s key management guidance in SP 800-57 sets out why cryptographic material needs a defined lifetime, and the same logic applies to any long-lived secret.

Where these  end up

Rarely in one place. A client secret typically lives in a configuration file on a server, in a pipeline variable, in the documentation somebody wrote during the build, and in a message thread from the day it was set up. Version control history is the one people forget: a secret committed by accident and removed in the next commit remains in the repository history for anyone with read access. Secret scanning across full history, rather than the current working tree, is the check that surfaces these, and it usually finds more than the team expects.

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Rotation without an outage

The reason secrets never rotate is that rotating them breaks things, so design for two valid credentials at once. Most identity platforms allow a second client secret or certificate to be added alongside the first, which lets you deploy the new value, confirm traffic is using it, and remove the old one afterwards. Build that sequence into a documented runbook and test it on a low risk integration first. Once the process is proven, an annual rotation becomes routine, and an emergency rotation after a suspected exposure becomes something you can do in an hour rather than a weekend.

“The question that decides how a bad day goes is whether you can revoke a partner credential without taking down your own service. Practise it before you need it. I have watched teams delay revocation for a full day during a live incident because nobody knew what would break, and the attacker was using that credential the entire time.”

William Fieldhouse, Director, Aardwolf Security Ltd

Removing the secret altogether

The strongest answer is not to hold one. Workload identity federation lets a pipeline or a workload prove what it is to your identity provider and receive a short-lived token, with no stored key anywhere. Managed identities do the same within a cloud platform. Certificate-based authentication is a good middle ground where federation is unavailable, since certificates expire by design and force a renewal process into existence. Each of these turns credential hygiene from a discipline you have to maintain into a property of the platform.

Checking what is actually in use

Inventory every credential with its owner, the systems that use it, the permissions it grants and the date it was last changed. Then check usage: an integration credential that has not authenticated in six months is either dormant or being used by something you have forgotten. Include these paths in API penetration testing engagements, since testers will look for keys in client-side code, in mobile applications and in repositories. Pair that with vulnerability assessments of the systems holding the secrets, because a compromised server hands over every credential stored on it regardless of how well it was chosen.

Frequently asked questions about machine credentials

These questions come up whenever a secrets management project starts.

How often should client secrets be rotated?

Annually as a baseline, and immediately when someone with access to them leaves or when exposure is suspected. Frequency matters less than having a rehearsed process, since an untested annual rotation tends not to happen.

Are environment variables a safe place for secrets?

They are better than a file in the repository and worse than a vault. Anything that can read the process environment can read them, including crash dumps and diagnostic endpoints, so treat them as a step on the way rather than the destination.