Threat Modeling: Anticipating and Mitigating Security Risks

 

What is Threat Modeling?

Threat Modeling is a structured process by which potential threats, such as structural vulnerabilities or the absence of appropriate safeguards, can be identified, quantified, and prioritized. The process often involves the use of diagrams to visualize the attack surface, and a catalogue of common threats to identify potential security issues.

Benefits of Threat Modeling

Implementing threat modeling brings numerous advantages, including:

• Improved understanding of security requirements and system behavior
• Prioritization of threats and security efforts
• Enhanced communication about security within the team
• Reduction in the overall risk for the project or system

Key Components

Effective threat modeling relies on understanding three key components:

• Assets: What you’re trying to protect.
• Threat Agents: Who or what might attack your systems.
• Security Controls: Measures to mitigate risk.

Threat Modeling Process

The process can typically be broken down into several stages:

1. Define security requirements.
2. Create an architecture overview of the system.
3. Decompose the system to understand the data flow and entry points.
4. Identify potential threats.
5. Document threats and rate their severity.
6. Identify mitigations against those threats.

Tools and Techniques

Here are two commonly used ones:

1. STRIDE:
   • Definition: STRIDE is an acronym that represents six different types of threats that a system might face. The categories include Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, and Elevation of Privilege.
   • Usage: During threat modeling, each component of the system is analyzed for potential threats falling into one or more of these categories. This structured approach helps in systematically identifying and categorizing threats.
   • Example:
     • Spoofing: Unauthorized users attempting to log in using someone else’s credentials.
     • Tampering: Modification of data in transit between the client and server.
     • Repudiation: Users denying that they performed a particular action.
     • Information Disclosure: Unauthorized access to sensitive information.
     • Denial of Service: Overloading the system with requests to make it unavailable.
     • Elevation of Privilege: Unauthorized users gaining higher-level access.
2. Attack Tree Diagrams:
   • Definition: Attack trees are graphical representations of potential attacks on a system. They are hierarchical structures that break down a complex threat scenario into a tree-like structure, starting with the primary goal of the attacker and branching out into different ways the goal can be achieved.
   • Usage: Attack trees provide a visual representation of attack paths and help in understanding the relationships between different attack vectors. This can be useful for prioritizing and strategizing mitigation efforts.
   • Example:
     • Primary Goal: Gain unauthorized access to a user’s profile.
     • Attack Paths:
       • Exploiting a session management vulnerability.
       • Performing a successful phishing attack to obtain login credentials.
       • Exploiting a cross-site scripting (XSS) vulnerability to steal session cookies.
       • Brute-force attacks on weak passwords.

These tools and techniques are not mutually exclusive and can be used together to enhance the overall threat modeling process. The STRIDE framework helps categorize threats, while attack tree diagrams provide a visual representation of potential attack scenarios. By combining these approaches, security professionals can gain a comprehensive understanding of the threats their system might face and develop effective mitigation strategies.

Best Practices

Some best practices include:

• Start early in the development lifecycle.
• Engage a diverse team with different skill sets.
• Keep models simple and understandable.
• Update models as systems evolve.

Threat Modeling for a simple Web Application

Consider a simple web application with basic functionality: login, profile management, and logout. Here’s a step-by-step process, accompanied by code examples, on how to approach threat modeling for such an app.

1. Data Transmission Security:

   • Threat: Man-in-the-Middle (MitM) attacks could intercept data transmitted between the client and server during login or profile update.
   • Mitigation: Implement HTTPS to encrypt data in transit. Ensure that sensitive information, such as login credentials, is transmitted over a secure connection.

2. Authentication:

   • Threat: Brute force attacks on the login page.
   • Mitigation: Implement account lockout mechanisms after a certain number of failed login attempts. Use strong password policies, and consider implementing multi-factor authentication for an additional layer of security.

3. Session Management:

   • Threat: Session hijacking or session fixation attacks.
   • Mitigation: Use secure, randomly generated session tokens. Implement session timeout mechanisms and regenerate session tokens upon login or privilege elevation.

4. Cross-Site Scripting (XSS):

   • Threat: Attackers inject malicious scripts into user inputs, which can be executed by other users.
   • Mitigation: Sanitize and validate user inputs. Use Content Security Policy (CSP) headers to prevent unauthorized script execution.

5. Cross-Site Request Forgery (CSRF):

   • Threat: Attackers trick users into performing actions on the application without their consent.
   • Mitigation: Use anti-CSRF tokens in forms to ensure that requests are only accepted from authenticated and authorized users.

6. Data Validation and Sanitization:

   • Threat: Inadequate validation of user inputs could lead to SQL injection or other data manipulation attacks.
   • Mitigation: Use parameterized queries or prepared statements to prevent SQL injection. Validate and sanitize all user inputs to prevent other forms of injection attacks.

7. Insecure Direct Object References (IDOR):

   • Threat: Users may manipulate URLs or other parameters to access unauthorized data.
   • Mitigation: Implement proper access controls and validation checks to ensure that users can only access their own data.

8. Insecure Session Storage:

   • Threat: Storing sensitive information (such as passwords) insecurely on the client side.
   • Mitigation: Use secure session storage mechanisms, avoid storing sensitive information on the client side, and hash and salt passwords before storage.

9. Error Handling:

   • Threat: Revealing sensitive information through error messages.
   • Mitigation: Customize error messages to provide minimal information to users. Log detailed errors for developers but display user-friendly messages to end-users.

10. Security Updates:

• • Threat: Running outdated software with known vulnerabilities.
  • Mitigation: Regularly update and patch the application, server, and dependencies to address known security vulnerabilities.

Conclusion

Threat Modeling is a critical exercise for anticipating and countering potential security threats in software systems. By identifying threats, determining risks, specifying countermeasures, and implementing those mitigations, developers can significantly reduce the vulnerability of applications. Using threat modeling tools further aids this process by providing structured methodologies and automated assistance to ensure comprehensive coverage of potential security risks. Developers should make threat modeling an integral part of the development lifecycle to maintain robust, secure applications.

References

• OWASP SAMM (Software Assurance Maturity Model)
• IriusRisk – Threat Modeling Tool
• ThreatModeler
• OWASP Threat Dragon
• PyTM – Pythonic Threat Modeling
• OWASP Foundation. (n.d.). OWASP Threat Modelling Project. OWASP. https://owasp.org/www-community/Threat_Modeling
• Microsoft Security Development Lifecycle. (n.d.). Threat Modeling. Microsoft. https://www.microsoft.com/en-us/securityengineering/sdl/threatmodeling