Threat Modelling

Threat modelling is a structured method to identify, analyze, and mitigate potential threats in systems, applications, or organizations. It helps teams uncover vulnerabilities early and build security into the design before attackers exploit weaknesses.

• Identifies what can go wrong before deployment
• Helps understand attacker goals, techniques, and entry points
• Prioritises risks based on impact and likelihood
• Ensures security becomes part of the development lifecycle

It can be applied to a wide range of targets such as:

• Software and applications
• Systems and networks
• Distributed systems and IoT devices
• Business processes

The Purpose of Threat Modeling

The purpose of threat modeling is to identify, communicate, and understand threats and mitigations for the organization's stakeholders as early as possible.

Key Components of a Threat Model

• Description of the subject being modeled
• Assumptions that can be validated or challenged over time
• Potential threats relevant to the system or environment
• Mitigation actions for each identified threat
• Validation steps to ensure mitigations are effective

Process of Threat Modeling

This process ensures that security is integrated into the design phase and maintained throughout the application’s lifecycle.

1. Define Scope & Objectives

Clarify what part of the system you're analyzing and why.

• Identifies what needs protection
• Defines assets, boundaries, and goals
• Establishes who makes security decisions

2. Diagram the System

Create a visual map of components and data flows.

• Shows how users and systems interact
• Highlights data movement and trust boundaries
• Exposes areas where attacks may occur

3. Identify Threats

Determine what can go wrong in the system.

• Reveals attacker entry points and techniques
• Uses STRIDE or similar frameworks
• Maps threats to assets and workflows

4. Analyze & Prioritize Risks

Rank threats based on impact and likelihood.

• Focuses attention on critical risks
• Helps estimate real-world damage potential
• Supports informed decision-making

5. Design Mitigations

Plan security measures to reduce or eliminate threats.

• Defines clear mitigation actions
• Aligns controls to specific threats
• Strengthens overall system resilience

6. Review & Iterate

Continuously refine the model as the system evolves.

• Validates existing controls
• Updates diagrams as architecture changes
• Ensures ongoing security alignment

Threat Modelling Methodologies

The development team will be able to implement application security as part of the design and development process by using threat modeling to identify threats, risks, and mitigation during the designing phase.

1. STRIDE

A Microsoft model that categorizes threats into six major security areas.

• Spoofing → pretending to be someone/something else
• Tampering → altering data or system components
• Repudiation → denying actions without evidence
• Information Disclosure → unauthorized data exposure
• Denial of Service → making services unavailable
• Elevation of Privilege → gaining higher-than-allowed permissions

2. DREAD

A risk-rating system used to score threats based on severity and impact.

• Damage Potential → how severe the impact is
• Reproducibility → how easily the attack can be repeated
• Exploitability → difficulty of launching the attack
• Affected Users → number of users impacted
• Discoverability → how easy it is to find the weakness

3. PASTA (Process for Attack Simulation and Threat Analysis)

A 7-stage methodology focused on attacker behavior and real-world attack scenarios.

• Models threats from attacker’s perspective
• Aligns system architecture to possible attack paths
• Helps design strong, risk-based security controls

4. Trike

A risk-management–oriented model that defines acceptable risk levels for assets.

• Uses stakeholder requirements
• Maps actions, roles, and asset permissions
• Prioritizes threats based on defined risk boundaries

5. VAST (Visual, Agile, and Simple Threat Modeling)

A scalable approach designed for large enterprises and agile teams.

• Uses visual models for applications and infrastructure
• Integrates easily into development workflows
• Does not require deep security knowledge

6. Attack Tree

A visual diagram showing all possible ways an attacker can reach a goal.

• Hierarchical structure with AND/OR logic
• Helps analyze multiple attack paths
• Supports structured reasoning about attack feasibility

7. CVSS (Common Vulnerability Scoring System)

A standardized scoring method to rate vulnerability severity (0–10).

• Uses metrics like impact, exploitability, complexity
• Helps prioritize vulnerability patching
• Offers consistent, industry-wide scoring

8. T-MAP

A modeling method used for COTS systems using UML diagrams.

• Identifies asset vulnerabilities and attack paths
• Calculates risk based on asset–threat relationships
• Supports structured evaluation for packaged systems

Tools for Threat Modelling

These tools help automate and streamline the threat modeling process, enabling teams to identify, assess, and mitigate security risks more efficiently throughout the software development lifecycle.

1. Microsoft's Threat Modelling Tool
2. MyAppSecurity
3. IriuRisk
4. securiCAD
5. SD Elements by Security Compass
6. Modeling Attack Trees
7. CVSS 3.0
8. Tiramisu

How To Create a Threat Model

All threat modeling processes start with creating a visual representation of the application or system being analyzed. There are two ways to create a visual representation: 

1. Visual Representation Using Data Flow Diagrams (DFD)

DFDs show how data moves, is stored, and is processed within a system.

• Used by Microsoft Methodology, PASTA, and Trike
• Originated in the 1970s; trust boundaries added in early 2000s for security use
• Helps classify threats using methods like STRIDE

• Focuses on viewing the system like an adversary, characterizing components, and identifying threats
• Highlights data movement but does not accurately represent real user behavior
• Often inconsistent because no standard method exists
• Different people may produce very different models for the same system
• Limited threat identification → often a weak starting point

2. Visual Representation using Process Flow Diagram

PFDs were introduced in 2011 to overcome DFD limitations and better support Agile teams. They focus on how attackers move through the application, not just data flow.

• Models the application from the attacker’s viewpoint
• Focuses on abusing normal user actions to reach assets
• Used by the VAST methodology
• Represents user interactions, transitions, and controls (forms, cookies, protocols, etc.)
• Easy to understand and does not require security expertise
• Produces a clear process map showing how a user or attacker that navigates the system

PFD-based threat models view applications from the perspective of user interactions. Following are the steps for PFD-based threat modelling: 

1. Designing application's use cases
2. The communication protocols by which individuals move between use cases are defined
3. Including the various technical controls – such as forms, cookies, etc
4. PFD-based threat models are easy to understand and don't require any security expertise.
5. Creation of process map -showing how individuals move through an application. Thus, it is easy to understand the application from the attacker's point of view.

Threat Modelling Best Practices

Threat modelling fosters a shared understanding of security across the entire team and serves as the first step toward making security a collective responsibility. To get the most value from it, follow these five key best practices when creating or updating your threat model.

• Involve the entire team (dev, security, ops, product)
• Understand the system fully before modeling
• Focus on the highest-value assets and threats
• Iterate regularly as the system evolves
• Document risks and track mitigations to closure
• Validate assumptions through testing (pentests, code reviews, fuzzing)
• Use consistent templates and scoring methods to ensure repeatable results