tfsec-policy

Overview

Important migration note per tfsec-home:

"tfsec is transitioning to Trivy, Aqua Security's consolidated scanning solution. The project documentation notes: 'Going forward we want to encourage the tfsec community to transition over to Trivy.'"

For new projects: evaluate Trivy first. tfsec remains stable for existing usage.

When to use

• Existing tfsec project; team isn't ready to migrate to Trivy.
• Terraform-only stack; want a focused Terraform-specific scanner.
• A specific tfsec rule covers something Trivy doesn't yet.

Step 1 - Install

# macOS
brew install tfsec

# Linux
curl -L https://github.com/aquasecurity/tfsec/releases/latest/download/tfsec-linux-amd64 \
  -o /usr/local/bin/tfsec
chmod +x /usr/local/bin/tfsec

Step 2 - Run

# Scan current directory
tfsec .

# Scan specific path
tfsec ./terraform/

# Concise output
tfsec . --concise-output

# Specific severity threshold
tfsec . --minimum-severity HIGH

Step 3 - Output formats

Per tfsec-home: "JSON and SARIF output capabilities for integration with external tools and workflows."

# JSON
tfsec . -f json > tfsec.json

# SARIF (GitHub Code Scanning)
tfsec . -f sarif -O tfsec.sarif

# JUnit XML
tfsec . -f junit -O tfsec.xml

# Markdown (PR comments)
tfsec . -f markdown

Step 4 - Skip checks

# Skip specific checks
tfsec . -e aws-s3-enable-bucket-encryption,aws-s3-enable-versioning

# Skip everything matching a pattern
tfsec . -e aws-s3-*

Inline:

# main.tf
resource "aws_s3_bucket" "public_data" {
  # tfsec:ignore:aws-s3-enable-bucket-encryption Public dataset, not encrypted by design
  # tfsec:ignore:aws-s3-enable-bucket-logging Public CDN, no audit logging needed
  bucket = "my-public-data"
  acl    = "public-read"
}

Step 5 - Custom rules

# .tfsec/custom_checks.yml
checks:
  - code: CUS001
    description: Ensure all EC2 instances have a cost_center tag
    impact: Untagged resources cannot be allocated to cost centers
    resolution: Add a cost_center tag
    requiredTypes:
      - resource
    requiredLabels:
      - aws_instance
    severity: HIGH
    matchSpec:
      name: tags
      action: contains
      value: cost_center
    errorMessage: EC2 instance is missing cost_center tag

Step 6 - CI integration

jobs:
  tfsec:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v5
      - uses: aquasecurity/tfsec-action@v1.0.3
        with:
          additional_args: --minimum-severity HIGH
          format: sarif
          output_file_path: tfsec.sarif
      - uses: github/codeql-action/upload-sarif@v3
        if: always()
        with:
          sarif_file: tfsec.sarif

Step 7 - Supported clouds

Per tfsec-home:

"AWS: API Gateway, EC2, S3, RDS, IAM, Lambda, and 30+ additional services

Azure: App Service, Storage, Database, Container, Key Vault, and others

Google Cloud: Compute, GKE, SQL, Storage, IAM, BigQuery, and more

Additional support includes Kubernetes, OpenStack, Oracle, DigitalOcean, and CloudStack environments."

For unsupported clouds, fall back to OPA / Conftest with custom Rego per policy-as-code-runner.

Step 8 - Migration to Trivy

Per tfsec-home guidance:

# Install Trivy
brew install trivy   # or apt-get / etc.

# Trivy includes tfsec's checks under `trivy config`
trivy config ./terraform/

The migration is mostly mechanical - Trivy ingests the same .tf files; rule names may differ.

Step 9 - Combine with Checkov + KICS

Per iac-policy-checker: multiple scanners catch overlapping but non-identical issues. tfsec is faster and Terraform-specific; Checkov is broader; KICS adds different rule classes.

tfsec . -f json > tfsec.json
checkov -d . -o json > checkov.json
kics scan -p . --report-formats json
# iac-policy-checker agent unifies results

Anti-patterns

Limitations

• Terraform-only. Doesn't scan Kubernetes / Dockerfile / CloudFormation directly (Trivy expands).
• Maintenance pace slowing. Per tfsec-home, focus is on Trivy; tfsec gets bug fixes but not new features.
• Some new cloud services lag in coverage. Newer AWS / Azure resources may not have rules yet.
• No baseline support out of the box. Adopt against legacy via skip annotations or wrapper scripts.

References

• tfs - tfsec overview, transition-to-Trivy positioning, developer-friendly output, AWS / Azure / GCP / Kubernetes / OpenStack / Oracle / DigitalOcean / CloudStack support, JSON / SARIF output.
• checkov-policy, kics-policy - sister scanners.
• policy-as-code-runner - custom OPA / Rego policies (for unsupported clouds or custom rules).
• iac-policy-checker - combines results.