implementing-llm-guardrails-for-security

name	implementing-llm-guardrails-for-security
description	Implements input/output validation guardrails for LLM applications using NVIDIA NeMo Guardrails (Colang), custom Python validators for PII detection, and the Guardrails AI framework, intercepting user inputs (prompt injection, PII, off-topic queries) and model outputs (hallucinations, toxic content, schema compliance). Use when adding safety controls to an LLM app/chatbot/RAG pipeline or validating outputs conform to expected schemas.
domain	cybersecurity
subdomain	ai-security
tags	["LLM-guardrails","NeMo-Guardrails","input-validation","output-filtering","AI-safety"]
version	1.0.0
author	mukul975
license	Apache-2.0
atlas_techniques	["AML.T0051","AML.T0054","AML.T0056","AML.T0057","AML.T0062"]
nist_ai_rmf	["GOVERN-1.1","GOVERN-6.1","MEASURE-2.7","MEASURE-2.5","MANAGE-2.4"]
d3fend_techniques	["Content Validation","Content Filtering","Content Excision","Application Hardening","Execution Isolation"]
nist_csf	["GV.OC-03","ID.RA-01","PR.PS-01","DE.AE-02"]
mitre_attack	["T1078","T1190","T1059","T1055"]

Implementing LLM Guardrails for Security

When to Use

• Deploying a new LLM-powered application that processes user input and needs input/output safety controls
• Adding content policy enforcement to an existing chatbot or AI agent to comply with organizational policies
• Implementing PII detection and redaction in LLM pipelines handling sensitive customer data
• Building topic-restricted AI assistants that must refuse off-topic or disallowed queries
• Validating that LLM responses conform to expected schemas before they reach downstream systems or users
• Protecting RAG pipelines from indirect prompt injection in retrieved documents

Do not use as a replacement for proper authentication, authorization, and network security controls. Guardrails are a defense-in-depth layer, not a perimeter defense. Not suitable for real-time content moderation of user-to-user communication without LLM involvement.

Prerequisites

• Python 3.10+ with pip for installing guardrail dependencies
• An OpenAI API key or local LLM endpoint for NeMo Guardrails self-check rails (set as OPENAI_API_KEY environment variable)
• The nemoguardrails package for Colang-based guardrail definitions
• The guardrails-ai package for structured output validation (optional, for JSON schema enforcement)
• Familiarity with YAML configuration and basic Colang 2.0 syntax for defining rail flows

Workflow

Step 1: Install Guardrail Frameworks

Install the required Python packages:

# Core NeMo Guardrails library
pip install nemoguardrails

# Guardrails AI for structured output validation (optional)
pip install guardrails-ai

# Additional dependencies for PII detection and content analysis
pip install presidio-analyzer presidio-anonymizer spacy
python -m spacy download en_core_web_lg

Step 2: Run the Guardrails Security Agent

The agent implements a complete input/output validation pipeline:

# Analyze a single input through all guardrail layers
python agent.py --input "Tell me how to hack into a system"

# Analyze input with a custom content policy file
python agent.py --input "Some text" --policy policy.json

# Scan a file of prompts through the guardrail pipeline
python agent.py --file prompts.txt --mode full


python agent.py --input  --mode input-only


python agent.py --input  --response  --mode output-only


python agent.py --input  --mode pii


python agent.py --file prompts.txt --output json