TLCTC Blog - 2025/03/18

Beyond STRIDE: The TLCTC Framework's Superior Approach to Cyber Threat Modeling

In the evolving landscape of cybersecurity, effective threat modeling frameworks are essential for organizations to identify, categorize, and mitigate potential security risks. Two significant frameworks in this domain are Microsoft's STRIDE and the newer Top Level Cyber Threat Clusters (TLCTC). While STRIDE has been a staple in security discussions for years, TLCTC offers a more robust, logically consistent approach to threat categorization. This blog post explores the key differences between these frameworks and why TLCTC represents a significant advancement in cybersecurity threat modeling.

Core Philosophical Differences

The fundamental difference between STRIDE and TLCTC lies in their underlying approach to threat categorization:

STRIDE: A Categorical Checklist

STRIDE is a mnemonic designed to help developers consider six categories of security threats:

• Spoofing identity
• Tampering with data
• Repudiation
• Information disclosure
• Denial of service
• Elevation of privilege

While useful as a quick reference, STRIDE lacks a comprehensive methodology explaining why these specific categories were chosen or how they relate to each other.

TLCTC: A Structured Taxonomy Based on Generic Vulnerabilities

TLCTC, in contrast, is built upon a set of clearly defined axioms and a rigorous thought experiment that systematically identifies generic vulnerabilities, resulting in ten distinct threat clusters. Each cluster represents a unique avenue of attack based on a specific generic vulnerability:

1. Abuse of Functions: Manipulating legitimate software functionality for malicious purposes
2. Exploiting Server: Targeting vulnerabilities in server-side software
3. Exploiting Client: Targeting vulnerabilities in client-side software
4. Identity Theft: Acquiring and misusing legitimate credentials
5. Man in the Middle: Intercepting and potentially altering communication
6. Flooding Attack: Overwhelming system resources and capacity limits
7. Malware: Abusing the ability of software to execute foreign code
8. Physical Attack: Unauthorized physical interference with hardware
9. Social Engineering: Manipulating people into compromising security
10. Supply Chain Attack: Compromising third-party components

Critical Limitations of STRIDE from a TLCTC Perspective

1. Mixing of Disparate Concepts

The most significant weakness of STRIDE is its conflation of different conceptual categories:

• Attacker Actions/Techniques: Spoofing and Tampering are actions an attacker performs
• Outcomes/Impacts: Information Disclosure and Denial of Service are results of successful attacks
• Security Properties: Repudiation relates to system auditability, not a threat itself
• Mixed Concepts: Elevation of Privilege can describe both method and outcome

TLCTC avoids this confusion by maintaining a consistent focus on the cause side of threats—the generic vulnerability being exploited—while clearly separating threats from their consequences.

2. Failure to Distinguish Between System Risk Events and Data Risk Events

A crucial advancement in TLCTC is its implementation of the bow-tie model for risk analysis, which clearly distinguishes between:

• System Risk Event (Central Event): The point where a threat successfully materializes, resulting in "Loss of Control" or "System Compromise"
• Data Risk Events (Consequences): The outcomes that may follow a system compromise:
  • Loss of Confidentiality (C): Data stolen
  • Loss of Integrity (I): Data modified
  • Loss of Availability (A): Data inaccessible

STRIDE fails to make this critical distinction, often treating what TLCTC would consider data risk events (like Information Disclosure) as threats themselves. This conflation makes it difficult to establish clear cause-and-effect relationships and implement appropriate controls.

The separation in TLCTC creates a critical "detection window" between initial compromise and subsequent data risk events, enabling more effective detection and response strategies. This distinction is operationally significant because:

1. It reflects the reality of modern attacks, where adversaries often maintain persistence before executing their ultimate objectives
2. It enables more precise mapping of detective and reactive controls in the period between compromise and data risk events
3. It acknowledges that some threats can lead to immediate data risk events, requiring rapid response capabilities

3. Ambiguity and Overlap in Categories

Because STRIDE mixes concepts, its categories frequently overlap, creating confusion about where particular threats should be classified. For example, Microsoft's own documentation lists "Threat #4" as simultaneously falling under three STRIDE categories (Spoofing identity, Information disclosure, and Elevation of privilege).

TLCTC's distinct clusters, based on non-overlapping generic vulnerabilities, eliminate this ambiguity. Each threat is categorized based on the initial vulnerability being exploited, providing clarity even in complex attack scenarios.

4. Incomplete Coverage

STRIDE's lack of a foundational methodology makes it difficult to assess its completeness. The framework doesn't provide a systematic way to determine if all possible threats are covered.

TLCTC, derived from a comprehensive thought experiment designed to cover all IT assets, makes a stronger claim to completeness. Its systematic derivation process ensures that each generic vulnerability is addressed by exactly one threat cluster.

5. Limited Actionability

The STRIDE categories are too broad and inconsistent to map directly to specific security controls. "Tampering," for example, could involve everything from SQL injection to altering network packets, making it challenging to translate STRIDE analysis into concrete security measures.

TLCTC, by focusing on the generic vulnerability, provides a clearer path to control implementation. For instance, identifying a threat as #2 Exploiting Server immediately guides you toward server-side code security, input validation, and web application firewalls.

How TLCTC Addresses STRIDE's Concerns

Despite STRIDE's categorization flaws, it raises valid security concerns that TLCTC effectively addresses:

Advanced Capabilities of TLCTC Not Present in STRIDE

TLCTC offers several capabilities that STRIDE simply doesn't address:

1. Attack Sequence Representation

TLCTC can represent complex attack paths using a standardized notation (e.g., #9->#3->#7), illustrating how threats can chain together. This provides crucial context for understanding sophisticated attacks and implementing appropriate defensive measures at each stage.

2. Strategic-Operational Bridge

TLCTC explicitly connects strategic risk management with operational security, offering a two-tiered approach:

• Strategic Layer: High-level risk management, policy-making, and program governance
• Operational Layer: Detailed security control implementation, monitoring, and adjustment

3. Comprehensive Control Framework Integration

TLCTC seamlessly integrates with the NIST Cybersecurity Framework functions (Identify, Protect, Detect, Respond, Recover), enabling a structured approach to control implementation for each threat cluster.

Practical Application Example

Consider a phishing attack that leads to credential theft and eventual data exfiltration:

STRIDE categorization might be:

• Spoofing (the attacker uses stolen credentials)
• Information Disclosure (sensitive data is exposed)

This lacks clarity about the attack sequence and conflates the threat (phishing) with the outcome (information disclosure).

TLCTC categorization would be:

• Attack sequence: #9 (Social Engineering) -> #4 (Identity Theft) -> Data Risk Event: Loss of Confidentiality
• Clear separation between the threat components and the data risk event
• Precise mapping to appropriate controls at each stage

Conclusion

While STRIDE has served as a helpful high-level brainstorming tool for developers, TLCTC provides a more rigorous, consistent, and complete approach to threat categorization. By focusing on generic vulnerabilities, clearly separating threats from consequences, and enabling the representation of complex attack sequences, TLCTC offers significant advantages for modern cybersecurity risk management.

The bow-tie model implemented in TLCTC—with its clear distinction between system risk events and data risk events—provides operational clarity that STRIDE lacks. This framework bridges the gap between strategic risk management and tactical security operations, enabling organizations to develop more effective security strategies in an increasingly complex threat landscape.

For organizations seeking to move beyond checklists to a comprehensive, structured approach to threat modeling and risk management, TLCTC represents the clear path forward.