Terraform Security Best Practices

by Dan.C

Terraform Security Best Practices: Protecting Infrastructure-as-Code from Risks

Table of Contents

1. Why Terraform Security Matters
2. Use Least Privilege IAM for Terraform
3. Secure Terraform State Files
4. Scan Terraform Code for Vulnerabilities
5. Isolate Environments
6. Never Hardcode Secrets
7. Harden Your Terraform Modules
8. Review Changes Before Applying
9. Final Thoughts
10. Related Posts

Why Terraform Security Matters

Terraform is a powerful IaC (Infrastructure as Code) tool, but misconfigurations and insecure practices can open doors to serious security breaches. From leaked credentials to over-permissive IAM roles, poor Terraform hygiene is often the root cause of cloud compromise.

This post highlights the key security best practices that I’ve implemented in real-world environments to harden Terraform usage and minimize risk.

Use Least Privilege IAM for Terraform

Avoid using AdministratorAccess for your Terraform automation or local development.

• Create specific IAM roles for each environment (e.g., TerraformDevRole, TerraformProdRole).
• Restrict permissions to only the required actions.
• Use OIDC with GitHub Actions to eliminate long-lived credentials.

Tooling Tip:
Use terraform-aws-iam-policy-documents to generate principle-of-least-privilege policies easily.

Secure Terraform State Files

Terraform’s tfstate contains sensitive information such as:

• Secrets
• Resource ARNs
• IP addresses
• Keys and endpoints

Best practices:

• Use remote state backends like S3 with encryption, versioning, and access control.
• Enable DynamoDB state locking to prevent concurrent writes.
• Add *.tfstate* to .gitignore and never push to VCS.

Scan Terraform Code for Vulnerabilities

Automate security scanning of Terraform code before any deployment:

• Checkov
• TFSec
• KICS

checkov -d .

Integrate these into your CI/CD pipeline and fail builds on high-severity findings.

Isolate Environments

Avoid deploying different environments into the same workspace or backend.

• Use separate backends for dev, staging, and prod.
• Prefix resources with environment tags: prod-db, dev-vpc.
• Use different IAM roles and security policies per environment.

Never Hardcode Secrets

Hardcoded secrets can easily leak into version control.

Instead, use:

• Terraform variables loaded at runtime
• Secret managers like AWS Secrets Manager, HashiCorp Vault
• GitHub Actions/GitLab CI secrets injection (TF_VAR_)

Harden Your Terraform Modules

Keep modules modular, secure, and testable:

• Validate inputs (type, regex, etc.)
• Pin module versions with tags, not main
• Audit third-party modules before use

Review Changes Before Applying

Every terraform apply should go through:

• Manual or automated terraform plan review
• PR reviews with code owners or cloud security leads
• Git history with change context and reasoning

Final Thoughts

Security in Terraform isn’t optional — it’s foundational. Secure state, validated inputs, and least privilege access go a long way toward building safe and scalable infrastructure.

Want more? I’ll soon publish a secure AWS Terraform project template with built-in guardrails and automation.

Related posts

• Linux commands cheat Sheat
• Master TF fast - Guide + Cheat Sheet

Stay sharp, stay secure. — Dan.C