Threat modeling is a structured approach to identifying, understanding, and addressing potential security threats to a system during the design and development phases. It involves systematically analyzing what could go wrong with a system from a security perspective.

Key importance:

• Early Detection: Identifies vulnerabilities before code is written, making fixes cheaper
• Systematic Approach: Ensures comprehensive security analysis rather than ad-hoc testing
• Risk Prioritization: Helps focus security efforts on the most critical threats
• Communication: Provides a common language for discussing security with stakeholders
• Compliance: Often required for regulatory compliance and security standards

Example: Instead of discovering a SQL injection vulnerability during penetration testing, threat modeling would identify during design that user input flows to database queries without proper validation, allowing preventive measures to be implemented from the start.

STRIDE is a mnemonic developed by Microsoft for categorizing security threats into six main types:

• S - Spoofing: Impersonating someone or something else (authentication threats)
• T - Tampering: Modifying data or code (integrity threats)
• R - Repudiation: Claiming you didn't do something you actually did (non-repudiation threats)
• I - Information Disclosure: Exposing information to unauthorized parties (confidentiality threats)
• D - Denial of Service: Denying or degrading service to valid users (availability threats)
• E - Elevation of Privilege: Gaining capabilities without proper authorization (authorization threats)

Application Example: For a web login system:

• Spoofing: Attacker uses stolen credentials
• Tampering: Session cookies are modified
• Repudiation: User denies making a transaction
• Information Disclosure: Password database is leaked
• DoS: Login attempts overwhelm the server
• Elevation of Privilege: Regular user gains admin access through exploit

These are fundamental security concepts often confused but with distinct meanings:

Threat: A potential danger or adverse event that could harm a system

• External entity or circumstance that could cause harm
• Examples: Hackers, malware, natural disasters, insider threats

Vulnerability: A weakness or flaw in a system that could be exploited

• Security gaps in design, implementation, or configuration
• Examples: Unpatched software, weak passwords, missing access controls

Risk: The likelihood and impact of a threat exploiting a vulnerability

• Risk = Threat × Vulnerability × Impact
• Measurable in business terms (financial, reputation, operational)

Relationship Example:

• Threat: Malicious hacker (external threat actor)
• Vulnerability: Unpatched web server with known SQL injection flaw
• Risk: 70% probability of data breach within 6 months, estimated $2M impact

Risk Management: You can't eliminate threats, but you can reduce vulnerabilities and mitigate risks through security controls.