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SensePost Threat Modelling

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Presentation by Dominic White at Metricon 6 in 2011. …

Presentation by Dominic White at Metricon 6 in 2011.

This presentation is about the methodology behind Sensepost's corporate threat modeling tool.

Published in: Technology, Education

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  • Can we improve on qualitative risk assessments to provide a better view of how bag guys will attack you, but can we also extend the scope of what a pentest can achieve without extending the time. The CTM can also dictate a testing plan to make sure you test the “right” things, which would improve the accuracy but also the testing plan should allow a pentest to run faster as not everything is tested. The danger is that if you’ve made a bad assumption, the “find stuff we didn’t think of aspect” of the pentest could be lost.
  • Other tools didn’t give us what we need. Either didn’t give metrics we needed, required a view external consultants couldn’t easily get, took too long or just weren’t great.
  • The trust associated with a location is related to how much control we have over the actions performed by users in that organization. This can lead to some non-obvious scenarios at first glance. For example, administrative access has fewer controls by default than normal user access, and is hence less trusted. Specific technology to monitor and control admin access would increase this trust. The fact that administrators are more trusted would be represented on the user not the location. * Different applications part of the same system will get different logical *locations* and possibly different network interfaces, but not different functional interfaces (as locations represent control, interface represents a full compromise of a system) * Make sure all unauthenticated location have a high level of trust, since you can't do anything on them (we assume)
  • The trust afforded to a user should ideally be based on ability to monitor their actions, employee screening lengths, contractual remediations etc. For example, super users are generally considered more trusted, but quite frequently only because of the position and seniority they occupy, not for solid codified reasons.
  • Interface values must be consistent throughout, unless an interface exposes much less value than the entire system. For example, if a system is critical to the business, and if the web application to access it only exposes a subset of functionality, it would still be possible to compromise that interface to provide full value and the less functionality can be represented by the likelihood and impact under risk. Even an NTP interface (especially if it runs as SYSTEM or an administrative user and has a history of buffer overflows) should mirror the value of the system.
  • Removed reference to automated system locations
  • <Name> - <Description> Locations #Places interfaces and users exist Physical #Physical places such as offices or data centers Network #Network locations such as internal net or DMZ Functional #Authorization levels within a system e.g. Administrative, Authenticated & Unauthenticated access. This represents the controls in place for members of this role. Interfaces #Means of accessing a system Physical #Physical means such as hardware, or the console Network #Electronic communication means such as RDP or NTP Functional #Authorization levels within a system e.g. Administrative, Authenticated & Unauthenticated access. This represents the functionality & data members with this role would have access to. Users #Actors utilizing systems or relevant to the threat model Admins #Administrators of the system, keep it specific to the system not supporting infrastructure Users #Normal users of the system Support #Who supports the system/application, are they different from the administrators AA #How authentication & authorization are handled Authentication Source #Where are usernames & passwords stored, and what is checked when a user logs in Authorization #How is access within the app managed e.g. externally via AD groups, or internal to the App Integration #How does it connect to other systems. Focus on attack paths Source #How does it receive data Destination #Where does it send it to Criticality #How important to the business is this system Confidentiality #How critical is keeping the data secret Integrity #How critical is keeping the data accurate Availability #How critical is the uptime
  • Interlinking 1) e.g. an Oracle DBA may be able to access the administrative functionality of an app being hosted on it 2) Push, pull, full. If data is pushed from a system to another, then the source will have access to the destination and the destination’s functional interface will be exposed at the source’s functional location
  • 2 vs. 3 tier: With 2-tier, if you access to the app, then you have DB access. 3-tier, access doesn’t imply DB access.
  • But, measuring threat and vulnerability is somewhat difficult, so we measure likelihood.
  • Latex to generate the equation: \\left(AttackLikelihood \\times \\frac{(6-UserTrust)+(6-LocationTrust)}{2}\\times 0.2 \\right) + \\left(InterfaceValue \\times Impact \\times 0.2\\right ) use at http://www.codecogs.com/latex/eqneditor.php
  • Transcript

    • 1. Metricon 6, a Usenix Workshop
      SensePostThreat Modeling
    • 2. Agenda
      Introduction
      What is TM
      Why TM
      Our goals with CTM
      Methodology
      Entities & Mapping
      Modeling
      Risk Calculation & Permutations
      Analysis
      Scenario Modeling
      Brief Comparisons
    • 3. Dominic White
      @singe
      http://singe.za.net/
      Work:
      Research:
      MSc in Security
      Interests in Privacy, Defensive Tech & Security Management
      About Me
    • 4. Introduction
      What is TM
      Why TM
      Design Goals
      1
    • 5. A model in science is a physical, mathematical, or logical representation of a systemof entities, phenomena, or processes.
      Basically a model is a simplified abstract view of the complex reality
      Breadth over depth
      Represents criteria specific to analysis
      What is Modeling?
    • 6. A threat model is:
      “A systematic, non-provable, internally consistent method of modeling a system, enumerating risks against it, and prioritising them.”
      Systematic
      Non-Provable
      Internally Consistent
      System Model
      Risk Enumeration
      Prioritisation
      What is Threat Modeling?
    • 7. Escaping the Detail Trade Off
    • 8. Usual Drivers of Controls
      Audit reports
      Prioritises: financial systems, audit house priorities, auditor skills, rotation plan, known systems
      Vendor marketing
      Prioritises: new problems, overinflated problems, product as solution
      New Attacks
      Prioritises: popular vulnerability research, complex attacks
      Individual Experience
      Prioritises: past experience, new systems, individual motives
      Why Threat Model?
    • 9. Threat Modeling provides:
      All (most) information security risks
      systematic enumeration of risks
      Prioritisation of risks
      puts known risks in their place & compares new risks
      Justification
      no appeal to expert authority
      Decision Making
      scenario modeling to test decisions
      Education
      Can involve whole team
      Why Threat Model?
    • 10. Developed for consultative role
      i.e. likely not the person making the changes
      Focus is on:
      Providing decision making information
      Rapid initial model creation
      Hybrid approach
      Bit of all the others
      Some parts we just threw out
      Highly flexible
      Initially, due to uncertainty, increasingly less so
      Detailed & aggregated results
      Includes test plan for verification
      SensePost CTM Design Goals
    • 11. Methodology
      Entities & Mappings
      2.1
    • 12. Entity Overview
      Locations
      Controls
      Users
      enforceable trust
      Interfaces
      method of system access
      asset value
      Attacks
      likelihood
      Damage
      Tests
      certainty
      relevance
    • 13. Represent the trust (controls) of a location
      Interfaces are exposed at locations
      Users are present at locations
      Three types:
      Physical
      Data centers, Head Office, Remote Sites
      Network
      Internet, DMZ, Server Network, User Network
      Logical / Functional (new)
      Represent controls within authorisation levels
      Administrative, authenticated, unauthenticated access
      Locations
    • 14. Enforceable trust of user group
      i.e. contractual or controlled trust, not gut feel
      Users are mapped to locations
      Interfaces are exposed to users via locations
      Example general groups:
      Anonymous
      unidentified or unauthenticated users
      External Users
      suppliers, contractors
      Internal Employees
      application users, administrators, call center
      Users
    • 15. Methods of interacting with a system or asset
      They are things an attacker could compromise
      Exposes the value of asset
      Interfaces to the same system have a consistent value
      Value can be set to existing system criticality ratings
      Types
      Physical
      Console Access, Hardware
      Network
      Remote Desktop, SSH, NTP
      Functional (new)
      Represent access to data & functionality within an authorisation role
      Administrative Access, Approve Transaction
      Interfaces
    • 16. Users are present at certain locations
      Many to Many mapping
      Both are a representation of controls
      “Company founder in the mission impossible room”
      vs..
      “Unknown Outsider on the Internet”
      Location type mappings
      Physical – users who can be physically present
      Network – users who can access the network
      Logical – users who have been granted, or have authorisation
      MappingUsers to Locations
    • 17. Interfaces are present at certain locations
      Many to Many mapping
      Constraints
      Physical interfaces only mapped to physical locations
      Physical Server in Data Centre A
      Technical interfaces only mapped to network locations
      Remote Desktop in Internal Network
      Functionality interfaces only to functional locations
      Execute Trade in Broken Role
      MappingInterfaces to Locations
    • 18. Attacks
      An attack in performed on an interface to expose some of its value
      Likelihood is based on factors specific to the attack
      Excludes trust of users, or controls in place
      General likelihood defined per attack, but made specific when mapped
      Popularity, easy of discovery/exploitation, prevalence (DREAD)
      Initial work into using external attack metrics
      VERIS – best mapping, sometimes non-discreet
      CWE – too detailed, vulns specific, no “abuse of privilege”
      STRIDE – not specific enough
      Impact is the worst case scenario
      Defines how much of interface value would be affected (damage)
      Originally named “risks”
    • 19. Attacks are performed against interfaces
      Many to one mapping
      Likelihood & Impact made specific per mapping
      System CIA should be considered e.g. theft of e-mail may be more damaging to the CEO than the gardener
      “Could this attack lead to a full compromise of the system?”
      Examples
      Physical theft of the Physical Server
      Password Bruteforce against Outlook Web Access Web Front-End
      Abuse of Privilege of the Administrator Role
      MappingAttacks to Interfaces
    • 20. Validate permutations of threat vector combinations
      Can be any type of test that provides more information
      Technical test, research, policy work
      Different tests provide a different level of certainty
      Proved  Disproved
      Can be granularly mapped
      Against a specific entity or combination of entities
      Tests
    • 21. Methodology
      Modeling
      How-to
      System Template
      Guidelines
      2.2
    • 22. Data Gathering
      Collect as much information about the environment as you can. Network diagrams, key system documentation, existing risk/criticality analysis, past audit reports
      Interview
      Ideally, find a tech generalist with a good overview, then get specific, large company’s knowledge is more distributed
      Look to validate statements across interviews
      Get multiple “views” on criticality
      Testing
      Light testing to validate claims e.g. basic network footprintingor application use
      Passive collection
      Look for problems that should come out in the TM e.g. if they have regular & damaging virus outbreaks and the TM disagrees …
      ModelingA How-To
    • 23. System Template<Name> |<Description>
      AA
      Authentication Source
      Authorization
      Integration
      Source
      Destination
      Criticality
      Include overall rating, individual ratings & reasons
      Confidentiality
      Integrity
      Availability
      Possession
      Authenticity
      Utility
      Locations
      Physical
      Network
      Functional (controls)
      Interfaces
      Include number & locations
      Physical
      Network
      Functional (access)
      Users
      Include number & locations
      Admins
      Users
      Support
    • 24. Identify unique entitiesfrom completed system templates and general documentation – reconcile if differences
      Identify shared infrastructure & create new systems for them
      Map users & interfaces to locations
      Linked systems
      An application's functional interfaces should be mapped to its infrastructure’s functional locations
      For integrated systems, map functional interfaces to locations depending on access (push vs.. pull vs.. full)
      Process
    • 25. Keep everything equally specific
      Summarise when no meaningful security difference
      Don’t create interfaces per-system for shared infrastructure
      Don’t represent risks more than once
      e.g. Don’t map two interfaces to the same system to the same location unless they are different “paths” e.g. administrator access implies “normal” access
      Avoid catch-all systems such as “user’s computers” rather model them as interfaces to relevant areas
      2-tier vs.. 3-tier applications have different access from the application to the DB & vice-versa
      Modeling Gotchas
    • 26. Methodology
      Calculations & Permutations
      2.3
    • 27. Entity Relationship
      present at
      available at
      performed at
      performed on
      performed by
    • 28. Permutations
      Administrators
      Exchange MAPI
      Head Office
      Remote MAPI
      Exploit
      Anonymous
    • 29. Understand concepts in relation to each other
      Discrete
      Individually necessary
      Collectively sufficient
      risk = threat x vulnerability x impact
      Disclaimer: Σ – The International Sign for “Stop Reading Here”
      Risk Equation
    • 30. The tool gives us the following inputs
      User Trust
      Location Trust (controls)
      Interface Value
      Attack Likelihood
      Attack Impact
      But, complete freedom in defining how they are mashed up
      Input Values
    • 31. risk = threat x vulnerability x impact
      likelihood = threat x vulnerability
      risk = likelihood x impact
      Likelihood
    • 32. risk = applied likelihood + value at risk
      applied likelihood =
      attack likelihood (reduced by)
      user trust + location trust
      value at risk =
      value of asset (reduced by)
      amount of asset exposed by attack
      Risk Equation Used
    • 33. [6 minus] – Ratings are out of 5 & denote a positive trust value, we want the “distrust” value
      [multiply 0.2] – We want the trust & impact to moderate the likelihood & value
      [divide by 2] – We take an average of user & location trust (equally weighted)
      Risk Equation
    • 34. Methodology
      Analysis
      2.4
    • 35. Takes every permutation & provides analysis graphs & a risk curve
      Provides three things
      Risk Curve
      One view to rule them all
      Analysis Graphs
      Slice & Dice
      Detailed risk searching/pivot table
      Zoom
      Threat Model Dashboard
    • 36. Challenge was to provide management view
      Single number loses too much context
      Frequency graph of number of “risks” per severity level
      Risk Curve
    • 37. “Digital” version of risk curve, with ability to show risks per entity type
      Can view per “perspective”
      physical, technical, functional
      Can zoom into showing only risks relating to a specific system
      Can look at “pivot” risks, i.e. attacks available to someone once they have compromised a system
      Analysis Graphs
    • 38. Analysis Graphs ExampleAll Perspectives, by Attack
    • 39. Analysis Graphs ExampleAll Perspectives, by Interfaces
    • 40. Analysis Graphs ExampleAll Perspectives, by Users
    • 41. Analysis Graphs ExampleAll Perspectives, by Locations
    • 42. Analysis Graphs ExampleTechnical Perspectives, by Attack
    • 43. Analysis Graphs ExampleFunctional attacks from Active Directory
    • 44. Methodology
      Scenario Modeling
      2.5
    • 45. Area Under Review
    • 46. Risk Frequency
    • 47. Cumulative Risk per Location
    • 48. Cumulative Risk per Threat
    • 49. Suggested Change
    • 50. Resulting Risk Frequency
    • 51. Resulting Risk per Location
    • 52. Recommended Change
    • 53. Resulting Risk Frequency
    • 54. Tool re-write - aiming for
      cross platform
      enforcing certain design constraints e.g. physical <-> physical mappings only
      macro’ing time consuming tasks
      Adding population size
      Permutations favour specificity e.g. if you define multiple user groups for one application & not another, the first app has more risks
      Refining the risk equation
      Equal consideration of user & location trust may need refining
      Normalise across physical, network & functional “views”
      Refining modeling bounding as results are tested
      Future Work
    • 55. Questions?
      http://www.sensepost.com/blog/
      The End