A wildcard rule is an authorization statement that matches more resources or actions than a narrowly scoped rule would. Wildcards are useful for flexibility, but they also expand the effective access surface and need careful review because they can quietly over-grant privileges.
Expanded Definition
A wildcard rule is a broad authorization pattern that grants access based on a match expression rather than an exact resource, identity, or action. In NHI environments, that usually means service accounts, API keys, workload identities, or agent permissions can touch multiple endpoints, buckets, queues, or verbs with a single statement. The convenience is obvious: teams can move faster, reduce rule sprawl, and support dynamic infrastructure. The risk is just as obvious: the effective permission set becomes harder to reason about, audit, and contain.
Definitions vary across vendors when wildcard rules are embedded in policy languages, IAM templates, or agent tool schemas, so the safest interpretation is operational rather than theoretical. A rule is wildcarded if it expands access beyond a narrowly enumerated scope, even when it appears harmless in code review. That matters under frameworks such as NIST Cybersecurity Framework 2.0, which emphasises least privilege and access governance as continuous controls.
The most common misapplication is treating a temporary wildcard as acceptable “just for now,” which occurs when deployment shortcuts are left in place after the workload moves into production.
Examples and Use Cases
Implementing wildcard rules rigorously often introduces review overhead and slower change management, requiring organisations to weigh deployment speed against the cost of broader blast radius.
- A CI/CD service account is granted access to Ultimate Guide to NHIs-style environments with a pattern that matches all repositories in a project, instead of only the release repository.
- An agent is allowed to invoke all tools in a model context protocol integration, rather than only the read-only lookup and ticket-create actions it actually needs.
- An API gateway policy permits a token to call any verb on any resource path under a service namespace, creating a broad privilege surface that is difficult to test exhaustively.
- A storage policy uses a wildcard bucket selector for development and production, then the same pattern is copied into production without tenant or environment separation.
- A cloud role is written with a wildcard action match to speed onboarding, but the team later discovers it also covers administrative operations that were never intended.
These patterns are often discussed in relation to least privilege in NIST Cybersecurity Framework 2.0, but in practice the hard part is not policy syntax. It is proving that a wildcard cannot be abused by a compromised NHI, an over-permissive agent, or a future integration that was not present when the rule was written.
Why It Matters in NHI Security
Wildcard rules are especially risky in NHI estates because machine identities scale quickly and often carry privileged automation. NHIMG reports that 97% of NHIs carry excessive privileges, which means broad rules can amplify an already oversized access footprint. When a wildcard sits inside a service account policy, secrets manager role, or agent tool grant, compromise of one identity can cascade across many systems before detection.
This is why wildcard review is not only a design concern but a governance requirement. A broad rule can mask hidden dependencies, complicate offboarding, and make incident response slower because responders cannot easily tell which resources were actually reachable. The Ultimate Guide to NHIs notes that only 5.7% of organisations have full visibility into their service accounts, which makes unrestricted matching patterns even harder to inventory and justify. NIST CSF 2.0 reinforces the operational need to identify, protect, and monitor access paths rather than assume permissive patterns are harmless.
Organisations typically encounter the consequences only after a secrets leak, privilege abuse, or agent misuse, at which point the wildcard rule becomes operationally unavoidable to address.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 and OWASP Agentic AI Top 10 address the attack and risk surface, while NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-01 | Wildcard permissions often create excessive NHI access beyond intended scope. |
| NIST CSF 2.0 | PR.AC-4 | Least-privilege access control requires limiting broad pattern-based authorization. |
| OWASP Agentic AI Top 10 | AGENT-03 | Agent tool access must avoid overly broad patterns that expand execution authority. |
Replace broad wildcard grants with explicit, testable NHI permissions and review them continuously.
Related resources from NHI Mgmt Group
- What is the difference between behavioural analytics and traditional rule-based monitoring?
- Why does the 72-hour breach reporting rule matter for IAM and security teams?
- What do security teams get wrong about wildcard redirect URIs?
- How should security teams govern bulk sensitive data transfers under the DOJ rule?
