# I built a prompt injection defense middleware for LLMs (Python/FastAPI)

> Source: <https://github.com/JustiNoel/LLM-Prompt-Injection>
> Published: 2026-07-13 16:54:16+00:00

**Production-grade LLM prompt injection defense middleware.**

PromptShield sits between your users and your AI model, detecting and blocking adversarial attacks before they cause damage.

PromptShield runs every user input through 4 layers of defense:

| Layer | Name | What It Does |
|---|---|---|
| 1 | Input Classifier | Detects malicious prompt patterns |
| 2 | Context Sanitizer | Strips injected instructions from user input |
| 3 | Prompt Integrity Checker | Validates prompt structure hasn't been tampered with |
| 4 | Output Monitor | Scans AI responses for signs of successful injection |

- ✅ 100% attack detection, zero false positives (benchmark tested)
- ⚙️ Tunable aggression dial —
`permissive`

→`balanced`

→`strict`

→`paranoid`

- 🔑 API key authentication + rate limiting
- 📊 Audit logging and dashboard UI
- 🐍 Python SDK for easy integration
- 🐳 Docker support

```
git clone https://github.com/JustiNoel/LLM-Prompt-Injection.git
cd LLM-Prompt-Injection
docker-compose up
```

Python · FastAPI · Google Gemini · Docker

Built by [Justin Noel](https://github.com/JustiNoel)