Distrust Threat Model

Unlike conventional frameworks (e.g., STRIDE, PASTA) that focus on identifying and mitigating specific risks, the Distrust Threat Model, rather than modeling threats as potential risks, assumes that systems are already compromised. This pessimistic, assumption-driven approach focuses on building systems that can survive and remain secure even when critical components fail or are actively under attack by sophisticated threat actors at all levels.

Assumptions

All screens and displays are assumed to be observable by adversaries.
Input devices, such as keyboards, are assumed to be monitored or logged by potential attackers.
Any system components (firmware or bootloaders) not verified on every boot are considered at risk.
Network-connected systems and administrative endpoints are potential compromise points.
Insider threats are assumed; some personnel or third-party maintainers may be compromised.
Physical attacks are viable and likely, given the history of supply chain and infrastructure breaches.
Side-channel attacks (similar to those observed with Spectre/Meltdown) represent realistic threats.

Levels

While the end-goal is to adequately address the risks which stem from the assumptions, organizations are at varying levels of maturity and often need a path towards mitigating threats in a phased approach. To this end, the threat model defines 4 levels, each corresponding to increasingly more sophisticated threat actors as the levels increase. Each threat actor is assumed to have access to specific methods of attack limited by factors such as cost to execute, sophistication, time required etc.

It is a reasonable approach to apply different threat model levels to different parts of systems. It's also worth noting that essentially no companies, to our knowledge meet adequate controls for Level 4 adversaries except for select nation states organizations and militaries.

Level 1

Adversary

An unskilled or lightly skilled individual leveraging widely available tools and publicly known vulnerabilities. Their attacks are largely opportunistic and automated, rather than targeted.

Attacks

Scanning for and exploiting known vulnerabilities with public exploits.
Phishing attempts using off-the-shelf kits.
Basic malware deployment (e.g., ransomware-as-a-service).

Level 2

Adversary

A skilled and resourceful individual specifically targeting a single organization. This adversary employs focused efforts to breach systems, including sophisticated social engineering and exploitation of newly disclosed vulnerabilities.

Attacks

Focused spear-phishing campaigns against key personnel.
Rapid exploitation of vulnerabilities shortly after public disclosure ("N-day" exploitation).
Man-in-the-middle (MitM) attacks against poorly secured communications.
Injection of malicious code into development pipelines.

Level 3

Adversary

An organized, well-funded group possessing diverse expertise across multiple domains (malware, supply chain, network exploitation, physical access, insider recruitment). Capable of sustained campaigns combining internal and external compromise.

Attacks

Coercion or recruitment of internal personnel ("insider threats").
Exploiting sophisticated zero-day vulnerabilities against internet-connected components.
Persistence and lateral movement after initial breach.
Coordinated, multi-stage attacks across digital and physical realms.

Level 4

Adversary

A state-backed or similarly resourced entity capable of executing the most advanced forms of cyber and physical attacks, including full-spectrum operations across the supply chain, hardware, firmware, and human factors..

Attacks

Supply chain compromise of hardware, firmware, or software prior to deployment.
Physical relocation of assets for tampering (e.g., interdiction of shipments).
Advanced side-channel attacks (e.g., Differential Fault Analysis, TEMPEST attacks).
Data remanence extraction techniques targeting decommissioned or wiped systems.
Sophisticated deception and counter-forensics to evade detection.