Threat Model Generation

Generate a comprehensive security threat model for a repository using the STRIDE methodology.

When to Use This Skill

• •First-time setup - New repository needs initial threat model
• •Architecture changes - Significant changes to components, APIs, or data flows
• •Security audit - Periodic review or compliance requirement
• •Manual request - Security team requests updated threat model

Inputs

Instructions

Step 1: Analyze Repository Structure

Scan the codebase to understand the system:

1. •

   Identify languages and frameworks

   • •Check package.json, requirements.txt, go.mod, Cargo.toml, etc.
   • •Note the primary tech stack
2. •

   Map components and services

   • •Look for apps/, services/, packages/ directories
   • •Identify entry points: API routes, CLI commands, web handlers
   • •Note databases, caches, message queues
3. •

   Identify external interfaces

   • •HTTP endpoints (REST, GraphQL)
   • •File upload handlers
   • •Webhook receivers
   • •OAuth/SSO integrations
4. •

   Trace data flows

   • •How does user input enter the system?
   • •Where is sensitive data stored?
   • •What external services are called?

Step 2: Identify Trust Boundaries

Define security zones:

1. •

   Public Zone (untrusted)

   • •All external HTTP endpoints
   • •Public APIs without authentication
   • •User-uploaded files
2. •

   Authenticated Zone (partially trusted)

   • •Endpoints requiring valid session/token
   • •User-specific data access
   • •Rate-limited APIs
3. •

   Internal Zone (trusted)

   • •Service-to-service communication
   • •Admin-only endpoints
   • •Database connections
   • •Secrets management

Step 3: Inventory Critical Assets

Classify data by sensitivity:

1. •

   PII (Personally Identifiable Information)

   • •User emails, names, addresses, phone numbers
   • •Document protection measures
2. •

   Credentials & Secrets

   • •Password hashes, API keys, OAuth tokens
   • •JWT signing keys, encryption keys
3. •

   Business-Critical Data

   • •Transaction records, customer data
   • •Proprietary algorithms, trade secrets

Step 4: Apply STRIDE Analysis

For each major component, analyze threats:

S - Spoofing Identity

• •Can attackers impersonate users or services?
• •Are authentication mechanisms secure?

T - Tampering with Data

• •Can attackers modify data in transit or at rest?
• •Look for: SQL injection, XSS, mass assignment, missing input validation

R - Repudiation

• •Can users deny actions they performed?
• •Look for: missing audit logs, insufficient logging

I - Information Disclosure

• •Can attackers access data they shouldn't?
• •Look for: IDOR, verbose errors, hardcoded secrets

D - Denial of Service

• •Can attackers disrupt service availability?
• •Look for: missing rate limits, resource exhaustion

E - Elevation of Privilege

• •Can attackers gain unauthorized access levels?
• •Look for: missing authorization checks, role manipulation

Step 5: Document Vulnerability Patterns

Create a library of code patterns specific to this codebase's tech stack.

Step 6: Generate Output Files

Create two files:

1. .factory/threat-model.md

Comprehensive threat model with:

• •System overview with architecture description
• •Trust boundaries and security zones
• •Attack surface inventory
• •Critical assets classification
• •STRIDE threat analysis for each component
• •Vulnerability pattern library
• •Security testing strategy
• •Assumptions and accepted risks
• •Version changelog

2. .factory/security-config.json

{
  "threat_model_version": "1.0.0",
  "last_updated": "<ISO timestamp>",
  "security_team_contacts": [],
  "compliance_requirements": [],
  "scan_frequency": "on_commit",
  "severity_thresholds": {
    "block_merge": ["CRITICAL"],
    "require_review": ["HIGH", "CRITICAL"],
    "notify_security_team": ["CRITICAL"]
  },
  "vulnerability_patterns": {
    "enabled": [
      "sql_injection",
      "xss",
      "command_injection",
      "path_traversal",
      "auth_bypass",
      "idor"
    ]
  }
}

Success Criteria

• • .factory/threat-model.md exists with all sections populated
• • .factory/security-config.json exists with valid JSON
• • All major components have STRIDE analysis
• • Vulnerability patterns match the tech stack
• • Document is written in natural language (LLM-readable)
• • No placeholder text remains

Example Invocations

Generate initial threat model:

Generate a threat model for this repository.

Update existing threat model:

Update the threat model - we added a new payments service.

Generate with compliance requirements:

Generate a threat model for this repository. We need to comply with SOC2 and GDPR.