How is an AI firewall different from a WAF?

A WAF blocks known HTTP attack patterns such as SQL metacharacters and XSS payloads by matching request structure. An AI firewall operates on the semantic content of prompts and model responses. A malicious instruction embedded inside a Word document that an AI agent reads looks like a normal HTTP request to a WAF, but an AI firewall can detect the injected instruction hidden inside the content. You need both controls, not one instead of the other.

What is indirect prompt injection?

Indirect prompt injection is an attack where malicious instructions are embedded in data the AI agent reads (emails, documents, web pages, retrieved chunks) rather than typed directly by the user. When the agent ingests that data, the injected instruction overrides the developer intent and can cause the agent to exfiltrate data, call unauthorized APIs, or take other damaging actions. It is the primary threat AI firewalls are designed to detect.

Which AI firewall is best for Microsoft Azure environments?

For organizations running Microsoft 365 Copilot or Azure OpenAI, Microsoft Defender for AI is the lowest-friction option because it integrates natively with Sentinel, Entra, and Purview. Its limitation is that it only covers Microsoft AI products. If your environment also includes direct OpenAI API calls, custom models, or third-party AI tools, a vendor-agnostic firewall such as Cisco AI Defense (formerly Lakera Guard) or Cloudflare Firewall for AI should run alongside Defender for AI.

Does an AI firewall add significant latency?

A well-optimized AI firewall adds roughly 20 to 50 milliseconds at the 99th percentile for synchronous chat applications. Vendors like Lakera Guard publish sub-50ms figures across their detection stack. Edge-based approaches like Cloudflare Firewall for AI run at the network edge to minimize added round trips. Async and batch AI workflows are generally tolerant of higher inspection latency, making them easier to protect without user-visible impact.

When do I not need an AI firewall?

If your AI integration is completely read-only and stateless, calling an LLM API only to transform user-submitted text with no access to internal data, no tool use, and no ability to take external actions, a WAF on the API endpoint may be sufficient. This scenario covers a shrinking share of enterprise AI deployments. Any agent that reads internal documents, calls internal APIs, or can send messages on behalf of users needs AI runtime inspection.

AI Security5 min read

What Is an AI Firewall? Runtime Protection for Enterprise AI in 2026

Q: What is an AI firewall?

An AI firewall is a security control that sits inline between users or upstream systems and a large language model, inspecting every prompt going in and every response coming out. It uses semantic classifiers to detect prompt injection, jailbreaks, PII leakage, and policy violations that traditional WAFs and NGFWs cannot identify because those tools work on HTTP structure, not natural language meaning.

AI firewalls inspect prompts and outputs in real time to block injection attacks, PII leakage, and jailbreaks that WAFs and NGFWs are blind to. Here is what they do, how leading vendors approach the problem, and how to evaluate one for your enterprise stack.

Idan Ohayon

June 21, 2026