On-the-fly access control is dynamic enforcement that applies policy during an active AI interaction. Rather than waiting for after-the-fact review, it can mask, redact, or block sensitive content in real time based on who is involved, what data is present, and the risk level of the exchange.
Expanded Definition
On-the-fly access control is a runtime decision layer for AI interactions and NHI workflows. It evaluates the current request, the identity or agent involved, the content being exchanged, and the policy context before allowing a response, revealing a secret, or continuing a tool action. That makes it different from static RBAC or periodic review, which only establish who should have access in general. In NHI environments, it is especially relevant where an AI agent, service account, or API client may encounter sensitive data mid-session and the correct decision depends on immediate context, not just preassigned role. The term is still evolving across vendors, and implementations vary between prompt filtering, data masking, response redaction, and hard blocking. NIST guidance on identity and access control, especially NIST SP 800-53 Rev 5 Security and Privacy Controls, supports this runtime enforcement model even if it does not use this exact phrase. The most common misapplication is treating a static policy rule as on-the-fly control, which occurs when teams inspect access only at login and ignore changes during the active exchange.
Examples and Use Cases
Implementing on-the-fly access control rigorously often introduces latency and policy complexity, requiring organisations to weigh stronger containment against a slower or more interrupted AI experience.
- An AI support agent receives a customer account number during a chat, and the system redacts the value before it reaches the model or downstream logs.
- A service account requests a secrets vault token mid-workflow, and access is granted only if the session risk, source workload, and intended action meet policy.
- An autonomous coding agent attempts to read production configuration, but the control blocks the prompt and returns a sanitized alternative.
- A SOC analyst reviews a sensitive incident transcript, while a runtime policy masks regulated fields unless the analyst’s current task explicitly requires them.
These patterns are closely related to the risks described in the Ultimate Guide to NHIs and the compromise scenarios in 52 NHI Breaches Analysis, where excess exposure often becomes visible only during a live interaction. For implementation guidance, teams commonly align these workflows with the OWASP Non-Human Identity Top 10 when defining runtime protections for AI and service identities.
Why It Matters in NHI Security
On-the-fly access control matters because NHI compromise is usually not a theoretical event. NHIMG reports that 80% of identity breaches involved compromised non-human identities such as service accounts and API keys, which means a live session can become the point of exposure rather than just the point of detection. Runtime enforcement helps limit what an agent can see, pass along, or execute after an identity has already been authenticated, which is critical when secrets, tokenized data, or tool outputs are being handled in motion. This is especially important in agentic systems where a single granted permission can cascade across multiple tool calls. The same operational logic is reflected in governance expectations from Ultimate Guide to NHIs — Key Challenges and Risks and the control expectations in Ultimate Guide to NHIs — Standards, where least privilege and continuous validation are core themes. Organisationally, the value of this control often becomes clear only after a secret is exposed, a tool is misused, or an agent returns data it should never have seen, at which point on-the-fly access control 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 address the attack and risk surface, while NIST CSF 2.0, NIST SP 800-63, NIST Zero Trust (SP 800-207) and NIST AI RMF set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-02 | Runtime masking and blocking reduce secret exposure and overbroad NHI access. |
| NIST CSF 2.0 | PR.AC-4 | Access permissions should be managed and enforced continuously, not only at login. |
| NIST SP 800-63 | Identity assurance informs whether a current session can be trusted for sensitive actions. | |
| NIST Zero Trust (SP 800-207) | Zero Trust requires continuous verification of identity, device, and session risk. | |
| NIST AI RMF | AI risk management covers runtime safeguards that shape model outputs and tool use. |
Apply contextual access decisions during sessions and review policies that allow excess runtime reach.
