Prompt firewall guide
How to prevent prompt injection before it reaches your LLM.
Preventing prompt injection requires more than a blacklist. Enterprises need a prompt firewall that combines detection, policy, sensitive data controls, and architecture patterns that reduce exposure.
Control
Policy first
Map every AI interaction to allow, flag, mask, or block decisions.
Traffic
Gateway aligned
Apply controls before prompts reach external model providers.
Evidence
Audit ready
Keep explainable records for security, risk, and compliance reviews.
Prevention starts with separating instructions, data, and policy.
Prompt injection succeeds when the model treats untrusted data as trusted instruction. Security teams should reduce that ambiguity with preflight inspection, retrieval controls, output constraints, and policy decisions that run outside the model.
Control
Real-time prompt inspection
Inspect user and system-bound prompts before provider dispatch.
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RAG
Secure RAG pipeline
Treat retrieved content as untrusted context and inspect it before model use.
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Architecture
LLM threat modeling
Map injection paths into your application and provider architecture.
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Use policy actions that match business risk.
Not every suspicious prompt should be handled the same way. Some should be blocked, some should be flagged, and some should be allowed with masking. PromptWall maps detection signals into allow, flag, mask, or block outcomes so teams can enforce without breaking legitimate workflows.
See PromptWall prevent prompt injection in practice
Walk through prompt injection scenarios and the policy actions that stop them.
Frequently asked questions
Can prompt injection be fully solved with prompting?+
No. Better system prompts help, but prevention requires controls outside the model, including inspection, policy, retrieval hygiene, and audit.
What is the fastest first control?+
Start with real-time prompt inspection and policy decisions for high-risk prompt categories, then expand into RAG and gateway controls.