Bidirectional Filtering with Runtime Guardrails
Security Requirement
A guardrails component SHOULD be deployed between the users/applications (or API gateway) and the models. This component acts as a gateway or proxy that inspects and acts on data flowing in both directions.
This skill refers to runtime guardrails (a deployed component), not model-level safety training.
Input Direction (User/App → Model)
Incoming prompts are raw or "tainted" input. The guardrails component analyzes them and applies rule-based actions:
| Action | Description |
|---|---|
| Block | Discard the prompt entirely, preventing it from reaching the model |
| Mask | Redact or obfuscate sensitive data (PII, credentials) before forwarding |
| Modify | Rewrite the prompt to remove dangerous patterns while preserving intent |
| Pass | Allow the prompt through unchanged |
Objectives:
- Prevent specific sensitive data from reaching the model
- Reduce the probability of prompt injection
- Enforce content policies on inputs
Output Direction (Model → User/App)
Model responses are inspected before delivery to the user or application:
| Action | Description |
|---|---|
| Block | Suppress the response if it contains harmful or policy-violating content |
| Mask | Redact sensitive data the model may have included in its response |
| Modify | Remove or rewrite problematic portions of the response |
| Pass | Deliver the response unchanged |
Objectives:
- Prevent leakage of sensitive training data
- Enforce content safety policies on outputs
- Filter harmful, biased, or off-topic responses
Architecture Position
User/App → API Gateway → Guardrails → Inference Engine → Model ↕ (inspects both directions) User/App ← API Gateway ← Guardrails ← Inference Engine ← Model
Implementation Checklist
- Deploy a guardrails component between the API gateway and the inference engine
- Configure input rules for prompt analysis (block, mask, modify, pass)
- Configure output rules for response analysis (block, mask, modify, pass)
- Define PII detection and masking rules for both directions
- Define prompt injection detection rules for the input direction
- Define content safety policies for the output direction
- Log all guardrail actions (blocks, masks, modifications) for audit
- Monitor guardrail effectiveness and tune rules based on observed patterns
- Ensure the guardrails component does not become a single point of failure (deploy with redundancy)
