Threat Modeling And Analysis

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This presentation is part of one of talk, I gave in Microsoft .NET Bootcamp. The contents are slightly edited to share the information in public domain. In this presentation, I covered the significance and all related theory of Threat modeling and analysis.This presentation will be useful for software architects/Managers,developers and QAs. Do share your feedback in comments.

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Threat Modeling And Analysis

  1. 1. Application Security-II Threat Modeling and Analysis Lalit Kale lalitkale@gmail.com http://lalitkale.wordpress.com
  2. 2. Overview • Introduction • Why Threat Modeling? • Application Decomposition • Threat Mapping • Calculating Risks • Planning Threat Response & Risk Mitigations • Best Practices in Threat Modeling • Tools • Resources 2
  3. 3. Introduction-Basic Terminology • Asset: A resource of value, such as the data in a database or on the file system. A system resource. • Threat: A potential occurrence, malicious or otherwise, that might damage or compromise your assets. • Vulnerability: A weakness in some aspect or feature of a system that makes a threat possible. Vulnerabilities might exist at the network, host, or application levels. • Attack (or exploit): An action taken by someone or something that harms an asset. This could be someone following through on a threat or exploiting a vulnerability. • Countermeasure: A safeguard that addresses a threat and mitigates risk. 3
  4. 4. What is Threat Modeling? • A Strategic framework for planning application security aspect in system design phase • Identify, understand, and mitigate threats most likely to affect the system • Can be practiced for both new applications as well as on existing ones 4
  5. 5. Why Threat Modeling? • Cannot build a secure system until you understand threats to system • Find security bugs early (and complex bugs) • Address threats in logical order according to greatest risk • Reduce overall risk by mitigating important threats • How do you know when application is “secure enough”? 5
  6. 6. Why Threat Modeling? • Helps better understand your application • Justification for security features and relation to identified threat • Clearly documented assumptions and/or consequences • Testers can specifically test against known threats • Helps prevent duplication of security efforts 6
  7. 7. Threat Modeling in Microsoft SDL 7
  8. 8. Types of Threat Modeling • Attacker Centric • • Software Centric • • Starts with an attack and evaluates the goals and how attackers might achieve them Starts from the design of system and attempts to step through a model of system, looking for types of attacks against each element of the model Asset Centric • Involves starting from assets entrusted to a system, such as a collection of sensitive personal information 8
  9. 9. Threat Modeling Phases Application Decomposition Threat Mapping Threat / Risk Rating Threat Response & Mitigations 9
  10. 10. Application Decomposition • Threat Response & Mitigations For instance, DFDs and Use Cases are useful • Threat / Risk Rating The type of diagram is not important, but it should focus on data and how it flows through the system • Threat Mapping Use modelling diagrams for a visual representation of how the subsystems operate and work together • Application Decomposition But don’t go too deep - 2 or 3 levels is enough 10
  11. 11. Application Decomposition 1. Logical architecture 5. Physical deployment 6. Technologies 7. Identify assets 8. Mark trust boundaries 9. Identify data flows, entry points, and assumptions 10. Threat Response & Mitigations Function 4. Threat / Risk Rating Create an architecture overview 3. Threat Mapping Define scope 2. Application Decomposition Make note of privileged code 11
  12. 12. Identifying Threats • Threat Response & Mitigations Compare application to common threats • Are Cross-Site Scripting (XSS) attacks relevant? • Is canonicalization an issue? • Can user sessions be hijacked? • … • Threat / Risk Rating Ask questions with regards to attacker goals • Can the user’s identity be spoofed? • Can data be accessed without authorization? • Can the system be easily blocked? • … • Threat Mapping Analyse each aspect of the architecture/design • Application Decomposition Use structured methods to identify threats 12
  13. 13. Identifying Threats Application Decomposition Threat Mapping Threat / Risk Rating Threat Response & Mitigations • To identify threats or goals, ask the following questions: • How can the adversary use or manipulate the asset to modify or control the system? • Retrieve information within the system? • Manipulate information within the system? • Cause the system to fail or become unusable? • Gain additional rights? • Can the adversary access the asset • Without being audited? • And skip any access control checks? • And appear to be another user? 13
  14. 14. STRIDE Model Application Decomposition Threat Mapping Threat / Risk Rating Threat Response & Mitigations • A common model for classifying attacker goals is the STRIDE model: • Spoofing – Posing as another user, component, or external system that should be identified by the system • Tampering – Unauthorized modification of data • Repudiation – Denying performing an action without the system being able to prove otherwise • Information Disclosure – Exposure of protected data to an unauthorized user • Denial of Service – Disallowing valid users to access the system • Elevation of Privileges – Gaining privileged access by a lower privileged user 14
  15. 15. Threat Tree Application Decomposition Threat Mapping Threat / Risk Rating Threat Response & Mitigations • Method to explore valid attack paths • Represents conditions needed to exploit the threat • Determine all the combined vulnerabilities associated with a threat • Focus on mitigating the vulnerabilities that form the “path of least resistance” 15
  16. 16. Documenting Threats • Application Decomposition Threat Mapping Threat / Risk Rating Threat Response & Mitigations Each threat should be documented with 1. Title 2. Target component 3. Vulnerability Categorization(s) (e.g. STRIDE) 4. Attack techniques (e.g. threat tree) 5. Risk 6. Mitigation 16
  17. 17. Calculating Risks: RPD Model • Application Decomposition Threat Mapping Threat / Risk Rating Threat Response & Mitigations How do I measure risk? • • Use a structured methodology Predefine general values to avoid confusion • Record the calculated risk • Simple formula: • Risk = Probability * Damage Potential • • • • Define expected damage for each value Divide scale in three bands: High, Medium, Low Simple, yet lacking dimension Not always easy to agree… 17
  18. 18. Calculating Risks: DREAD Model Application Decomposition Threat Mapping Threat / Risk Rating • Another method for determining risk is DREAD model • Damage potential – How great is the damage if the vulnerability is exploited? • Reproducibility – How easy is it to reproduce the attack? • Exploitability – How easy is it to launch an attack? • Affected users – As a rough percentage, how many users are affected? • Discoverability – How easy is it to find the vulnerability? • Risk = Min(D, (D+R+E+A+D) / 5) • Threat Response & Mitigations Agree beforehand on values of each factor 18
  19. 19. Threat Resolution & Risk Mitigation • Application Decomposition Threat Mapping Threat / Risk Rating Threat Response & Mitigations Threats can be resolved by • • • • Risk Acceptance - doing nothing Risk Transference - pass risk to an externality Risk Avoidance - removing the feature/component that causes the risk Risk Mitigation - decrease the risk • Mitigation strategies should be examined for each threat • Mitigations should be chosen according to the appropriate technology • Resolution should be decided according to risk level and cost of mitigations 19
  20. 20. Best Practices in Threat Modeling • Use structured & consistent methodologies • Predefine and agree on risk ratings that work for you • Include all relevant shareholders in TM discussions: • Security • Architecture / Design • Coding • • Testing Don’t let TM discussions to degenerate to finding solutions before the threats have been fully identified 20
  21. 21. Best Practices in Threat Modeling • Don’t model too deep – don’t get carried away in the details • Document TM results so they could be used later on for: • • Similar products / systems • • Next versions Education Use common attack libraries / patterns for consistency and additional ideas e.g. http://www.owasp.org/index.php/Category:Attack • Always remember – its never too late for Threat Modeling! 21
  22. 22. Threat Modeling Tools • The Threat Analysis and Modeling Tool (TAM): • is an asset-focused tool designed for LOB applications. • It is used for applications for which business objectives, deployment pattern, and data assets and access control are clearly defined. • The focus of the tool is to understand the business risk in the application, help identify controls needed to manage that risk, and protect the assets. 22
  23. 23. Threat Modeling Tools • The SDL Threat Modeling Tool: • is a software-focused tool designed for rich client/server application development (for example, Windows and SQL Server, among others) • The tool assumes the final deployment pattern of the product is unknown (that is, if it will be used to manage business-critical applications with customer credit cards or not), so the focus of the tool is to ensure security of the software’s underlying code. 23
  24. 24. Summary Application Decomposition •Define scope •Create an architecture overview •Function •Logical architecture •Physical deployment •Technologies •Identify assets •Mark trust boundaries •Identify data flows, entry points, and assumptions •Make note of privileged code Threat Mapping •Identifying Threats •Use STRIDE Model •Creating Threat Tree •Documenting each Threat Calculate Risks •Use Risk = Probability * Damage Potential •Use Risk = Min(D, (D+R+E+A+D) / 5) Threat Resolution and Risk Mitigation •Risk Acceptance - doing nothing •Risk Transference - pass risk to an externality •Risk Avoidance - removing the feature/component that causes the risk •Risk Mitigation - decrease the risk •Mitigation strategies should be examined for each threat •Mitigations should be chosen according to the appropriate technology •Resolution should be decided according to risk level and cost of mitigations 24
  25. 25. Resources • OWASP (Open Web Application Security Project): https://www.owasp.org • Microsoft Security: http://www.microsoft.com/security http://www.Microsoft.com/sdl • Wikipedia: http://en.wikipedia.org/wiki/Threat_model 25
  26. 26. Lalit Kale lalitkale@gmail.com http://lalitkale.wordpress.com . This presentation is shared under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International license. More information for this license is available at http://creativecommons.org/licenses/by-nc-sa/4.0/ All trademarks are the property of their respective owners. Lalit Kale makes no warranties, express, implied or statutory, as to the information in this presentation.

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