Advanced Threat Modeling

What is Threat Modeling?

Threat modeling is a structured approach to identifying potential security threats, vulnerabilities, and risks in a system. Rather than applying general security practices blindly, threat modeling helps you tailor security measures to your specific circumstances, adversaries, and risks.

For cryptographic systems like Secure Mail Client, threat modeling allows you to:

• Identify what you're trying to protect and from whom
• Determine which threats are most relevant to your situation
• Allocate security resources efficiently
• Make informed decisions about security trade-offs
• Evaluate whether specific security measures actually address your threats

The Threat Modeling Process

While there are various frameworks for threat modeling, we'll focus on a practical approach that works well for individuals and organizations using encrypted communication:

Step 1: Define Your Assets

Begin by identifying what you're trying to protect:

• Data assets - Email content, attachments, contact lists, metadata
• Cryptographic assets - Private keys, passphrases, key material
• Operational assets - Communication patterns, social connections, organizational structure
• System assets - Devices, applications, networks, physical infrastructure
• Reputation assets - Trust relationships, public perception, brand integrity

For each asset, determine:

• How valuable or sensitive is it?
• What would be the impact if it were compromised?
• Where is it stored, processed, or transmitted?

Step 2: Identify Adversaries and Their Capabilities

Consider who might target your assets and what resources they have:

• Mass surveillance - Intelligence agencies with vast technical capabilities but limited targeted focus
• Targeted state actors - Government entities specifically targeting you with significant resources
• Criminal organizations - Financially motivated actors with moderate technical capabilities
• Commercial entities - Companies interested in data for competitive or marketing purposes
• Hacktivists - Ideologically motivated groups with variable technical capabilities
• Malicious individuals - Former associates, stalkers, or others with personal motivations
• Automated threats - Malware, phishing campaigns, and other non-targeted threats

For each potential adversary, analyze:

• What are their motivations and goals?
• What technical capabilities do they possess?
• What resources (time, money, expertise) can they deploy?
• What access or insider information might they already have?
• How persistent are they likely to be?

Step 3: Analyze Potential Threats and Attack Vectors

Map out how adversaries might try to compromise your assets:

• Cryptographic attacks - Attempts to break or bypass encryption
• Endpoint compromise - Malware on devices accessing encrypted communications
• Physical access - Direct access to devices or hardware
• Network attacks - Man-in-the-middle, traffic analysis, metadata collection
• Social engineering - Phishing, pretexting, and other human-focused attacks
• Legal compulsion - Subpoenas, warrants, national security letters
• Side-channel attacks - Exploiting information leaked through timing, power consumption, etc.
• Supply chain attacks - Compromises in hardware, software, or services you depend on

Step 4: Evaluate Vulnerabilities and Risks

Assess where your systems might be vulnerable to the identified threats:

• Where do your assets have the greatest exposure?
• What security controls are already in place?
• What are the potential impacts if specific threats materialize?
• What is the likelihood of various attack scenarios?
• Which risks pose the greatest danger to your most important assets?

Step 5: Develop Mitigation Strategies

Create specific plans to address the identified risks:

• Prevention measures - Controls that reduce the likelihood of successful attacks
• Detection mechanisms - Systems to identify when attacks are occurring
• Response procedures - Plans for what to do when security is compromised
• Recovery capabilities - Methods to restore systems and data after incidents

For each mitigation:

• How effectively does it address the specific threat?
• What are the usability impacts or trade-offs?
• How reliable is the mitigation?
• What resources are required to implement and maintain it?

Practical Threat Modeling for Secure Mail Client Users

Let's apply these principles to develop a threat model for users of Secure Mail Client:

Example Scenario: Investigative Journalist

Consider a journalist working on stories involving corporate misconduct:

Assets

• Primary assets: Source identities, unpublished documents, interview notes, communication with editors
• Secondary assets: Personal reputation, organizational credibility, source trust

Adversaries

• Primary threat actors: Corporate security teams, private investigators, potentially corrupt officials
• Capabilities: Moderate technical resources, potential legal pressure, social engineering

Attack Vectors

• Targeted phishing to obtain account credentials
• Malware to compromise journalist's devices
• Legal demands for communication records from service providers
• Metadata analysis to identify sources
• Social engineering of contacts to gather information

Mitigation Plan

• Use Secure Mail Client with PGP for all source communications
• Implement hardware security keys for two-factor authentication
• Maintain a separate, air-gapped device for the most sensitive source management
• Use secure communication channels for initial contact that don't leave metadata trails
• Regular security training and awareness for both the journalist and key sources
• Develop an incident response plan in case of compromise

This module will be expanded with more detailed threat modeling examples and exercises in the future. For now, use this framework to begin developing your own threat model based on your specific circumstances.