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Versions: (draft-coffin-sacm-vuln-scenario) 00 01 02

SACM                                                           C. Coffin
Internet-Draft                                                B. Cheikes
Intended status: Informational                                C. Schmidt
Expires: March 13, 2017                                        D. Haynes
                                                   The MITRE Corporation
                                                     J. Fitzgerald-McKay
                                                   Department of Defense
                                                           D. Waltermire
                          National Institute of Standards and Technology
                                                       September 9, 2016


                 SACM Vulnerability Assessment Scenario
                    draft-ietf-sacm-vuln-scenario-02

Abstract

   This document describes an automated enterprise vulnerability
   assessment scenario aligned with the SACM Use Cases.  The scenario
   assumes the existence of endpoint management capabilities and begins
   with an enterprise ingesting vulnerability description information.
   Endpoints are assessed against the vulnerability description
   information based on a combination of examining known endpoint
   characterization information and collected endpoint information.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 13, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Assumptions . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Vulnerability Assessment Pre-requisites . . . . . . . . . . .   4
     4.1.  Endpoint Management Capabilities  . . . . . . . . . . . .   5
     4.2.  Vulnerability Description Information . . . . . . . . . .   5
   5.  Endpoint Vulnerability Assessment Capabilities  . . . . . . .   5
   6.  Vulnerability Assessment Results  . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  Informative References  . . . . . . . . . . . . . . . . . . .   7
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .   8
     A.1.  Changes in Revision -02 . . . . . . . . . . . . . . . . .   8
     A.2.  Changes in Revision -01 . . . . . . . . . . . . . . . . .   9
     A.3.  Changes Since Adopted as a WG I-D -00 . . . . . . . . . .   9
     A.4.  Changes in Revision draft-coffin-sacm-vuln-scenario-01  .  10
   Appendix B.  Implementation Examples  . . . . . . . . . . . . . .  11
     B.1.  Endpoint Data Collection  . . . . . . . . . . . . . . . .  11
     B.2.  Vulnerability Description Information . . . . . . . . . .  12
     B.3.  Secondary Assessment  . . . . . . . . . . . . . . . . . .  12
     B.4.  Assessment Results  . . . . . . . . . . . . . . . . . . .  13
   Appendix C.  Priority . . . . . . . . . . . . . . . . . . . . . .  13
   Appendix D.  SACM Usage Scenarios . . . . . . . . . . . . . . . .  14
   Appendix E.  SACM Requirements and Charter - Future Work  . . . .  16
   Appendix F.  SACM Use Case Alignment  . . . . . . . . . . . . . .  16
     F.1.  Endpoint Identification . . . . . . . . . . . . . . . . .  16
     F.2.  Endpoint Data Collection  . . . . . . . . . . . . . . . .  16
     F.3.  Vulnerability Description Information . . . . . . . . . .  17
     F.4.  Applicability . . . . . . . . . . . . . . . . . . . . . .  17
     F.5.  Secondary Assessment  . . . . . . . . . . . . . . . . . .  17
     F.6.  Assessment Results  . . . . . . . . . . . . . . . . . . .  18
   Appendix G.  Alignment with Other Existing Works  . . . . . . . .  18
     G.1.  Critical Security Controls  . . . . . . . . . . . . . . .  18
       G.1.1.  Continuous Vulnerability Assessment . . . . . . . . .  18
       G.1.2.  Hardware and Software Inventories . . . . . . . . . .  19
   Appendix H.  Continuous Vulnerability Assessment  . . . . . . . .  20



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   Appendix I.  Data Attribute Table . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

1.  Introduction

   This document describes a detailed, enterprise-specific vulnerability
   assessment scenario from which information model elements can be
   discovered.  This scenario also informs protocol and data model
   development in support of vulnerability assessment, as part of
   overall posture assessment (see Appendix B for examples of solutions
   that support this scenario).

   Vulnerability discovery, disclosure, publication, and prioritization
   is out of scope.  However, given the importance of prioritization in
   an enterprise's vulnerability assessment process, it is discussed in
   Appendix C.

   Information on how the scenario aligns with SACM and other existing
   work is discussed in Appendix D through Appendix G.

2.  Terminology

   Vulnerability description information:  Information pertaining to the
         existence of a flaw or flaws in software, hardware, and/or
         firmware, which could potentially have an adverse impact on
         enterprise IT functionality and/or security.  Vulnerability
         description information should contain enough information to
         support vulnerability detection.

   Vulnerability detection data:  A type of guidance extracted or
         derived from vulnerability description information that
         describes the specific mechanisms of vulnerability detection
         that is used by an enterprise's vulnerability management
         capabilities to determine if a vulnerability is present on an
         endpoint.

   Endpoint management capabilities:  An enterprise IT department's
         ability to manage endpoint identity, endpoint information, and
         associated metadata on an ongoing basis.

   Vulnerability management capabilities:  An enterprise IT department's
         ability to manage endpoint vulnerabilities and associated
         metadata on an ongoing basis by ingesting vulnerability
         description information and vulnerability detection data, and
         performing vulnerability assessments.

   Vulnerability assessment capabilities:  An enterprise IT department's
         ability to determine whether a set of endpoints is vulnerable



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         according to the information contained in the vulnerability
         description information.

3.  Assumptions

   A number of assumptions must be stated in order to further clarify
   the position and scope of this document.

   The document assumes that:

   o  The enterprise has received vulnerability description information,
      and that the information has already been processed into
      vulnerability detection data that the enterprise's security
      software tools can understand and use.

   o  The enterprise has a means of identifying enterprise endpoints
      through the execution of Target Endpoint Discovery Tasks although
      assertions about some details of this capability are made.

   o  The enterprise has a means of extracting relevant information
      about enterprise endpoints in a form that is compatible with the
      vulnerability description data.

   o  All information described in this scenario is available in the
      vulnerability description data and serves as the basis of
      assessments.

   o  The enterprise can provide all relevant information about any
      endpoint needed to perform the described assessment.

   o  The enterprise has a mechanism for long-term storage of
      vulnerability description information, vulnerability detection
      data, and vulnerability assessment results.

   o  The enterprise has a procedure for reassessment of endpoints at
      some point after initial assessment (see Appendix H for more
      information).

4.  Vulnerability Assessment Pre-requisites

   In order to successfully support the vulnerability assessment
   scenario, an enterprise needs to have the following capabilities
   deployed on their network and information readily available.








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4.1.  Endpoint Management Capabilities

   Endpoint management capabilities are assumed to be in place within
   the enterprise, and are expected to collect a minimum set of
   attributes from the endpoints under management via Collection Tasks
   and to establish an endpoint's identity within the scope of that
   domain.  Endpoint identity can be established by collecting certain
   identifying attributes, collectively known as the Target Endpoint
   Identifier, that allow for unique and persistent tracking of
   endpoints on the enterprise network.  Examples include, but are not
   limited to, IP address, MAC address, Fully Qualified Domain Names
   (FQDNs), pre-provisioned identifiers such as Globally Unique
   Identifiers (GUIDs) or copies of serial numbers, certificates,
   hardware identity values, or similar attributes.  To simplify the
   identification of an endpoint, a Target Endpoint Label may be created
   and assigned to refer to the Target Endpoint Identifier.  All of the
   information collected by the endpoint management capabilities is
   stored, with appropriate metadata (i.e. timestamp), in a central
   location and used to build up a Target Endpoint Characterization
   Record and Target Endpoint Profile via a Target Endpoint
   Characterization Task.  The endpoint management capabilities are
   expected to be performed on an ongoing basis, resulting in routine,
   or even event-driven, collection of basic endpoint information.

   See Appendix I for information-specific details.

4.2.  Vulnerability Description Information

   Vulnerability description information is expected to be periodically
   received by the enterprise.  Upon receipt, the vulnerability
   description information is expected to be assigned a unique tracking
   identifier, stored in a repository (with appropriate metadata) in raw
   form, and transformed into a machine-readable vulnerability detection
   data with unique tracking identifier understood by the components
   described by this scenario.  This transformed form can be referred to
   as the vulnerability detection data.  At some point, receipt and
   processing of vulnerability description data is expected to trigger
   the vulnerability assessment.

   See Appendix I for information-specific details.

5.  Endpoint Vulnerability Assessment Capabilities

   When new vulnerability description information is received by the
   enterprise, affected endpoints are identified and assessed.  The
   vulnerability is said to apply to an endpoint if the endpoint
   satisfies the conditions expressed in the vulnerability detection
   data.



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   A vulnerability assessment (i.e. vulnerability detection) is
   performed in two steps:

   o  Endpoint information collected by the endpoint management
      capabilities is examined by the vulnerability management
      capabilities through Evaluation Tasks.

   o  If the data possessed by the endpoint management capabilities is
      insufficient, a Collection Task is triggered and the necessary
      data is collected from the target endpoint.

   Vulnerability detection relies on the examination of different
   endpoint information depending on the nature of a specific
   vulnerability.  Common endpoint information used to detect a
   vulnerability includes:

   o  A specific software version is installed on the endpoint

   o  File system attributes

   o  Specific state attributes

   In many cases, the endpoint information needed to determine an
   endpoint's vulnerability status will have been previously collected
   by the endpoint management capabilities and available in a
   Repository.  However, in other cases, the necessary endpoint
   information will not be readily available in a Repository and a
   Collection Task will be triggered to collect it from the target
   endpoint.  Of course, some implementations of endpoint management
   capabilities may prefer to enable operators to perform this
   collection under certain circumstances, even when sufficient
   information can be provided by the endpoint management capabilities
   (e.g. there may be freshness requirements for information).

   The collection of additional endpoint information for the purpose of
   vulnerability assessment does not necessarily need to be a pull by
   the vulnerability assessment capabilities.  Over time, some new
   pieces of information that are needed during common types of
   assessments might be identified.  Endpoint management capabilities
   can be reconfigured to have this information delivered automatically.
   This avoids the need to trigger additional Collection Tasks to gather
   this information during assessments, streamlining the assessment
   process.  Likewise, it might be observed that certain information
   delivered by endpoint management capabilities is rarely used.  In
   this case, it might be useful to re-configure the endpoint management
   capabilities to no longer collect this information to reduce network
   and processing overhead.  Instead, a new Collection Task can be




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   triggered to gather this data on the rare occasions when it is
   needed.

   See Appendix I for information-specific details.

6.  Vulnerability Assessment Results

   Vulnerability assessment results present evaluation results along
   with sufficient context, so that appropriate action can be taken.
   Vulnerability assessment results are ideally stored for later use.

   See Appendix I for information-specific details.

7.  IANA Considerations

   This memo includes no request to IANA.

8.  Security Considerations

   This document provides a core narrative that walks through an
   automated enterprise vulnerability assessment scenario and is aligned
   with SACM "Endpoint Security Posture Assessment: Enterprise Use
   Cases" [RFC7632].  As a result, the security considerations for
   [RFC7632] apply to this document.  Furthermore, the data collected as
   part of the vulnerability assessment may provide attackers with
   useful information such as what software an enterprise is running on
   their endpoints.  As a result, organizations should consider properly
   protecting this information.

9.  Informative References

   [charter-ietf-sacm-01]
              Security Automation and Continuous Monitoring, "Charter,
              Version 1.0", October 2015,
              <https://datatracker.ietf.org/doc/charter-ietf-sacm/>.

   [critical-controls]
              Center for Internet Security, "Critical Security Controls,
              Version 6.0", <https://www.cisecurity.org/critical-
              controls.cfm>.

   [cvrf]     Industry Consortium for Advancement of Security on the
              Internet, "Common Vulnerability and Reporting Framework",
              May 2012, <http://www.icasi.org/cvrf/>.







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   [I-D.coffin-sacm-nea-swid-patnc]
              Coffin, C., Haynes, D., Schmidt, C., and J. Fitzgerald-
              McKay, "SWID Message and Attributes for PA-TNC", draft-
              coffin-sacm-nea-swid-patnc-01 (work in progress), June
              2016.

   [I-D.cokus-sacm-oval-results-model]
              Cokus, M., Haynes, D., Rothenberg, D., and J. Gonzalez,
              "OVAL(R) Results Model", draft-cokus-sacm-oval-results-
              model-01 (work in progress), September 2016.

   [I-D.hansbury-sacm-oval-info-model-mapping]
              mhansbury@mitre.org, m., Haynes, D., and J. Gonzalez,
              "OVAL and the SACM Information Model", draft-hansbury-
              sacm-oval-info-model-mapping-03 (work in progress),
              September 2016.

   [I-D.haynes-sacm-oval-definitions-model]
              Cokus, M., Haynes, D., Rothenberg, D., and J. Gonzalez,
              "OVAL(R) Definitions Model", draft-haynes-sacm-oval-
              definitions-model-01 (work in progress), September 2016.

   [I-D.ietf-sacm-requirements]
              Cam-Winget, N. and L. Lorenzin, "Security Automation and
              Continuous Monitoring (SACM) Requirements", draft-ietf-
              sacm-requirements-13 (work in progress), March 2016.

   [I-D.rothenberg-sacm-oval-sys-char-model]
              Cokus, M., Haynes, D., Rothenberg, D., and J. Gonzalez,
              "OVAL(R) System Characteristics Model", draft-rothenberg-
              sacm-oval-sys-char-model-01 (work in progress), September
              2016.

   [RFC7632]  Waltermire, D. and D. Harrington, "Endpoint Security
              Posture Assessment: Enterprise Use Cases", RFC 7632,
              DOI 10.17487/RFC7632, September 2015,
              <http://www.rfc-editor.org/info/rfc7632>.

Appendix A.  Change Log

A.1.  Changes in Revision -02

   Changed "capability" in the context of endpoint management,
   vulnerability management, and vulnerability assessments to
   "capabilities" to avoid confusion with the term "capability" in the
   terminology draft.

   Made a few other minor editorial and clarification changes.



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A.2.  Changes in Revision -01

   Clarified how the endpoint management capability can reconfigured
   over time to adapt to the needs of an enterprise.  GitHub issue #12
   (https://github.com/sacmwg/vulnerability-scenario/issues/12).

   Included references to the various appendices in the document.
   GitHub issue #18 (https://github.com/sacmwg/vulnerability-scenario/
   issues/18).

   Fixed typos and other minor editorial changes in the document.
   GitHub issue #19 (https://github.com/sacmwg/vulnerability-scenario/
   issues/18).  GitHub issue #20 (https://github.com/sacmwg/
   vulnerability-scenario/issues/20).  GitHub issue #22
   (https://github.com/sacmwg/vulnerability-scenario/issues/22).

   Updated references to the Critical Controls to Version 6.0.  GitHub
   issue #23 (https://github.com/sacmwg/vulnerability-scenario/
   issues/23).

   Aligned the scenario with SACM Tasks.  GitHub issue #25
   (https://github.com/sacmwg/vulnerability-scenario/issues/25).

A.3.  Changes Since Adopted as a WG I-D -00

   Made various organizational and editorial changes as proposed by Adam
   Montville.  GitHub issue #4 (https://github.com/sacmwg/vulnerability-
   scenario/issues/4).

   Removed the TODO from the Security Considerations section
   (https://github.com/sacmwg/vulnerability-scenario/issues/8).

   Clarified the definition of "vulnerability detection data" to explain
   how it was guidance and provided instructions for security tools on
   how to carry out a vulnerability assessment.  GitHub issue #13
   (https://github.com/sacmwg/vulnerability-scenario/issues/13).

   Changed "targeted collection" to "supplemental collection".  GitHub
   issue #14 (https://github.com/sacmwg/vulnerability-scenario/
   issues/14).

   Clarified that the ability for an enterprise to convert vulnerability
   description information and process it into a format usable by
   security tools is the same as the converting vulnerability
   description information into vulnerability detection data.  GitHub
   issue #15 (https://github.com/sacmwg/vulnerability-scenario/
   issues/15).




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   Determine if we need to remove references to the long-term storage of
   data in repositories.  GitHub issue #16 (https://github.com/sacmwg/
   vulnerability-scenario/issues/16).

   Moved the information needs captured in Appendix D.2 into the
   Information Model.  GitHub issue #17 (https://github.com/sacmwg/
   vulnerability-scenario/issues/17).

A.4.  Changes in Revision draft-coffin-sacm-vuln-scenario-01

   Clarification of the vulnerability description data IDs in sections 4
   and 6.

   Added "vulnerability remediation" to the Assessment Results and Data
   Attribute Table and Definitions sections.

   Added Implementation Examples to Endpoint Identification and Initial
   (Pre-Assessment) Data Collection, Vulnerability Description Data,
   Endpoint Applicability and Assessment, and Assessment Results
   sections.

   Added an example to vulnerability description data in the scope
   section.

   Added a sentence to clarify vulnerability description data definition
   in the scope section.

   Added data repository example for long-term storage scope item.

   Added sentence to direct reader to examples of basic system
   information in endpoint identification section.

   Split the examples of information to collect in the pre-assessment
   collection section into a basic and advanced list.

   Added examples of data stored in the repository in the Assessment
   Results section.

   Added sentence for human-assigned attributes in the Future Work
   section.

   Replaced "vulnerability report" to "vulnerability description data"
   because the term report was causing confusion.  Similarly, replaced
   "assessment report" with "assessment results".

   Replaced "Configuration Management Database (CMDB)" with "Repository"
   which is SACM's term for a data store.




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   Replaced endpoint "Role" with "Purpose" because "Role" is already
   defined in SACM.  Also, removed "Function" because it too is already
   defined in SACM.

   Clarified that the document does not try to define a normalized data
   format for vulnerability description data although it does not
   preclude the creation of such a format.

   Included additional examples of software configuration information.

   Clarified the section around endpoint identification to make it clear
   designation attributes used to correlate and identify endpoints are
   both persistent and unique.  Furthermore, text was added to explain
   how the persistency of attributes may vary.  This was based on
   knowledge gained from the Endpoint ID Design Team.

   Updated the Security Considerations section to mention those
   described in [RFC7632].

   Removed text around Bring Your Own Device (BYOD).  While important,
   BYOD just adds complexity to this initial draft.  BYOD should be
   addressed in a later revision.

   Merged the list of "basic endpoint information" and the list of
   "human-assigned endpoint attributes" as both represent data we want
   to collect about an endpoint.  Whether or not that data is natively
   available on the endpoint for collection or assigned by a human,
   computed, or derived from other data which may or may not be
   available on the endpoint for collection seems arbitrary.  With this
   scenario, we primarily care about expressing information needs rather
   than how the information is collected or from where.

Appendix B.  Implementation Examples

B.1.  Endpoint Data Collection

   Within the SACM Architecture, the Internal and External Collector
   components could be used to allow enterprises to collect posture
   attributes that demonstrate compliance with enterprise policy.
   Endpoints can be required to provide posture attributes, which may
   include identification attributes to enable persistent
   communications.

   The SWID Message and Attributes for PA-TNC standard
   [I-D.coffin-sacm-nea-swid-patnc] defines collection and validation of
   software identities using the ISO Software Identification Tag
   Standard.  Using this standard, the identity of all installed




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   software including the endpoint operating system, could be collected
   and used for later assessment.

   The OVAL Definitions Model [I-D.haynes-sacm-oval-definitions-model]
   provides a data model that can be used to specify what posture
   attributes to collect as well as their expected values which can be
   used to drive an assessment.

   The OVAL System Characteristics Model
   [I-D.rothenberg-sacm-oval-sys-char-model] can be used to capture
   information about an endpoint.  The model is specifically suited to
   expressing OS information, endpoint identification information (such
   as IP and MAC addresses), and other endpoint metadata.

B.2.  Vulnerability Description Information

   The Common Vulnerability Reporting Framework (CVRF) [cvrf] is an XML-
   based language that attempts to standardize the creation of
   vulnerability description information.  Using CVRF, the enterprise
   could create automated tools based on the standardized schema which
   would obtain the needed and relevant information useful for later
   assessments and assessment results.

B.3.  Secondary Assessment

   Within the SACM Architecture, the assessment task would be handled by
   the Evaluator component.  If previously collected data is used, it
   would be obtained from a Data Store component.

   Within the SACM Architecture, the Internal and External Collector
   components could be used to allow enterprises to collect posture
   attributes that demonstrate compliance with enterprise policy.
   Endpoints can be required to provide posture attributes, which may
   include identification attributes to enable persistent
   communications.

   The SWID Message and Attributes for PA-TNC standard defines
   collection and validation of software identities using the ISO
   Software Identification Tag Standard.  Using this standard, all
   installed software including the endpoint operating system could be
   collected and stored for later assessment.

   The OVAL Definitions Model provides a data model that can be used to
   specify what posture attributes to collect as well as their expected
   values which can be used to drive an assessment.

   The OVAL System Characteristics Model can be used to capture
   information about an endpoint.  The model is specifically suited to



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   expressing OS information, endpoint identification information (such
   as IP and MAC addresses), and other endpoint metadata.

   The SACM Internal and External Attribute Collector components can be
   used to allow enterprises to collect posture attributes that
   demonstrate compliance with enterprise policy.  Endpoints can be
   required to provide posture attributes, which may include
   identification attributes to enable persistent communications.

B.4.  Assessment Results

   The OVAL Results Model [I-D.cokus-sacm-oval-results-model] provides a
   data model to encode the results of the assessment, which could then
   be stored in a Repository and later accessed.  The assessment results
   described in this scenario could be stored and later accessed using
   the OVAL Results Model.  Note that the use of the OVAL Results Model
   for sharing results is not recommended per section 7.3 of the OVAL
   and the SACM Information Model
   [I-D.hansbury-sacm-oval-info-model-mapping].

   Within the SACM Architecture, the generation of the assessment
   results would occur in the Report Generator component.  Those results
   might then be moved to a Data Store component for later sharing and
   retrieval as defined by SACM.

Appendix C.  Priority

   Priorities associated with the vulnerability description information,
   assessment results, and any remedy is important, but is treated as a
   separate challenge and, as such, has not been integrated into the
   description of this scenario.  Nevertheless, it is important to point
   out and describe the use of priorities in the overall vulnerability
   assessment scenario as a separate issue with its own sets of
   requirements.

   Priority in regard to vulnerability description information, can be
   viewed in a couple of different ways within an enterprise.  The
   assessment prioritization involves prioritization of the
   vulnerability description information assessment process.  This
   determines what vulnerability description information is assessed,
   and in what order it is assessed in.  For instance, a vulnerability
   affecting an operating system or application used throughout the
   enterprise would likely be prioritized higher than a vulnerability in
   an application which is used only on a few, low-criticality
   endpoints.

   The prioritization of remedies relates to the enterprise remediation
   and mitigation process based on the discovered vulnerabilities.  Once



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   an assessment has been performed and applicable endpoints identified,
   enterprise vulnerability managers must determine where to focus their
   efforts to apply appropriate remedies.  For example, a vulnerability
   that is easily exploitable and which can allow arbitrary code
   execution might be remedied before a vulnerability that is more
   difficult to exploit or which just degrades performance.

   Some vulnerability description information include severities and/or
   other information that places the vulnerability in context.  This
   information can be used in both of the priority types discussed
   above.  In other cases, enterprise administrators may need to
   prioritize based only on what they know about their enterprise and
   the description provided in the vulnerability description
   information.

   Examples of data attributes specific to priority of assessments and/
   or remedies include (but not limited to) the following:

   o  Enterprise - defined purpose of the device, criticality of the
      device, exposure of the device, etc.

   o  Severity attributes - A rating or score that attempts to provide
      the level of severity or criticality associated with a given
      vulnerability.

   o  Cyber threat intelligence - information such as tactics,
      techniques, and procedures of threat actors, indicators of
      compromise, incidents, courses of action, etc. that help the
      enterprise understand relevant threats and how to detect,
      mitigate, or respond to them.

Appendix D.  SACM Usage Scenarios

   The SACM "Endpoint Security Posture Assessment: Enterprise Use Cases"
   document ([RFC7632]) defines multiple usage scenarios that are meant
   to provide examples of implementing the use cases and building block
   capabilities.  Below is a brief summary of some of these usage
   scenarios and how this document aligns and/or adds additional value
   to the identified usage scenarios.

   o  Automated Checklist Verification (2.2.2) - "An enterprise operates
      a heterogeneous IT environment.  They utilize vendor-provided
      automatable security configuration checklists for each operating
      system and application used within their IT environment.  Multiple
      checklists are used from different vendors to ensure adequate
      coverage of all IT assets."  The usage scenario, as defined in the
      RFC, is targeted at the checklist level and can be interpreted as
      being specific to endpoint configuration.  There is mention of



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      patch assessment and vulnerability mitigation, but the usage
      scenario could be expanded upon by including vulnerability
      verification.  Replacing the idea of a checklist in the SACM usage
      scenario with vulnerability would allow the usage scenario to
      align almost exactly with the scenario described in this document.
      Instead of collecting automatable security configuration
      checklists, the enterprise would collect automatable vulnerability
      description information available from the vendor as described or
      possibly from other interested third-parties.

   o  Detection of Posture Deviations (2.2.3) - "An enterprise has
      established secure configuration baselines for each different type
      of endpoint within their IT environment.  When an endpoint
      connects to the network, the appropriate baseline configuration is
      communicated to the endpoint.  Once the baseline has been
      established, the endpoint is monitored for any change events
      pertaining to the baseline on an ongoing basis.  When a change
      occurs to posture defined in the baseline, updated posture
      information is exchanged.  When the endpoint detects a posture
      change, an alert is generated identifying the specific changes in
      posture."  This usage scenario would support the concept of
      endpoints signaling or alerting the enterprise to changes in the
      posture relates to endpoint vulnerabilities in the same way that
      it would for configurations.  Replacing the idea of a checklist
      with vulnerability description data allows the SACM usage scenario
      and the scenario described in this document to align in their
      objectives.

   o  Asynchronous Compliance/Vulnerability Assessment at Ice Station
      Zebra (2.2.5) - "An isolated arctic IT environment that is
      separated from the main university network.  The only network
      communications are via an intermittent, low-speed, high-latency,
      high-cost satellite link.  Remote network admins will need to show
      continued compliance with the security policies of the university,
      the government, and the provider of the satellite network, as well
      as keep current on vulnerability testing."  This SACM usage
      scenario describes vulnerability assessment and aligns well with
      the vulnerability scenario described in this document.  The
      endpoint assets are identified and associated data is published in
      a Repository.  Vulnerability description information is collected
      and saved in a Repository as it is released.  The vulnerability
      description information is queued for later assessment, then the
      assessment results and vulnerability description information are
      stored after assessment.  The only real difference in this SACM
      usage scenario is the timing of the assessments.  The scenario
      described within this document would have no problems adjusting to
      the timing of this SACM usage scenario or anything similar.




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Appendix E.  SACM Requirements and Charter - Future Work

   In the course authoring this document, some additional considerations
   for possible future work were noted.  The following points were taken
   from the SACM Requirements [I-D.ietf-sacm-requirements], SACM Charter
   [charter-ietf-sacm-01], and SACM Use Cases ([RFC7632]) documents and
   represent work that may be necessary to support the tasks or goals of
   SACM going forward.

   o  The SACM requirements mentions "Result Reporting" with
      applications but no detail around what the assessment results data
      set should include.  In the case of vulnerability assessment
      results, context is important and details beyond just a Pass or
      Fail result are needed in order to take action.  A good example of
      this might be the Priority of the vulnerability itself and how
      many systems it affects within the enterprise.  With this in mind,
      it might be worthwhile to investigate a minimum data set or schema
      for assessment results.  The concern here is with vulnerability
      description data, but this could apply to other enterprise
      processes as well.

   o  The "Human-assigned endpoint attributes" mentioned previously in
      this scenario are touched on in the SACM use cases, but the topic
      could probably be explored in much more depth.  Enterprise policy
      and behaviors could be greatly influenced by endpoint attributes
      such as locations, how the endpoint is used, and criticality.
      When and how these data attributes are collected, as well as what
      the minimum or common set might look like, would be good topics
      for future related SACM work.  In addition, the storage of these
      attributes could be central (stored in a data repository) or they
      could be assigned and stored on the endpoints themselves.

Appendix F.  SACM Use Case Alignment

F.1.  Endpoint Identification

   This sub-step aligns with the Endpoint Discovery, Endpoint
   Characterization, and Endpoint Target Identification building block
   capabilities.  The alignment is due to the fact that the purpose of
   this sub-step is to discover, identify, and characterize all
   endpoints on an enterprise network.

F.2.  Endpoint Data Collection

   This sub-step aligns with the Data Publication building block
   capability because this section involves storage of endpoint
   attributes within an enterprise Repository.  This sub-step also
   aligns with the Endpoint Characterization and Endpoint Target



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   Identification building block capabilities because it further
   characterizes the endpoint through automated and possibly manual
   means.  There is direct alignment with the Endpoint Component
   Inventory, Posture Attribute Identification, and Posture Attribute
   Value Collection building block capabilities since the purpose of
   this sub-step is to perform an initial inventory of the endpoint and
   collect basic attributes and their values.  Last, there is alignment
   with the Collection Guidance Acquisition building block capabilities
   as the inventory and collection of endpoint attributes would be
   directed by some type of enterprise or third-party guidance.

F.3.  Vulnerability Description Information

   This step aligns with the Data Publication and Data Retrieval
   building block capabilities because this section details storage of
   vulnerability description information within an enterprise Repository
   and later retrieval of the same.

F.4.  Applicability

   This sub-step aligns with the Data Retrieval, Data Query, and Posture
   Attribute Value Query building block capabilities because, in this
   sub-step, the process is attempting to determine the vulnerability
   status of the endpoint using the data that has previously been
   collected.

F.5.  Secondary Assessment

   This sub-step aligns with the Data Publication building block
   capability because this section details storage of endpoint
   attributes within an enterprise Repository.  The sub-step also aligns
   with the Collection Guidance Acquisition building block capability
   since the vulnerability description information (guidance) drives the
   collection of additional endpoint attributes.

   This sub-step aligns with the Endpoint Characterization (both manual
   and automated) and Endpoint Target Identification building block
   capabilities because it could further characterize the endpoint
   through automated and possibly manual means.  There is direct
   alignment with the Endpoint Component Inventory, Posture Attribute
   Identification, and Posture Attribute Value Collection building block
   capabilities since the purpose of this sub-step is to perform
   additional and more specific component inventories and collections of
   endpoint attributes and their values.







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F.6.  Assessment Results

   This step aligns with the Data Publication and Data Retrieval
   building block capabilities because this section details storage of
   vulnerability assessment results within an enterprise Repository and
   later retrieval of the same.

Appendix G.  Alignment with Other Existing Works

G.1.  Critical Security Controls

   The Center for Internet Security's Critical Security Controls
   [critical-controls] includes security controls for a number of usage
   scenarios, some of which are covered in this document.  This section
   documents the alignment between the Center's controls and the
   relevant elements of the scenario.

G.1.1.  Continuous Vulnerability Assessment

   "CSC 4: Continuous Vulnerability Assessment and Remediation," which
   is described by the Center for Internet Security as "Continuously
   acquire, assess, and take action on new information in order to
   identify vulnerabilities, remediate, and minimize the window of
   opportunity for attackers."  The scenario described in this document
   is aligned with CSC 4 in multiple ways:

   CSC 4.1 applies to this scenario in that it calls for running
   regular, automated scanning to deliver prioritized lists of
   vulnerabilities with which to respond.  The scenario described in
   this document is intended to be executed on a continuous basis, and
   the priorities of both vulnerability description information and the
   remedy of vulnerabilities are discussed in the Priority section
   earlier in this document.

   This scenario assumes that the enterprise already has a source for
   vulnerability description information as described in CSC 4.4.

   Both CSC 4.2 and 4.7 are made possible by writing information to a
   Repository since this makes previously collected data available for
   later analysis.

   While this scenario does not go into the details of how
   prioritization would be calculated or applied, it does touch on some
   of the important ways in which prioritization would impact the
   endpoint assessment process in the Priority section.  As such, the
   Priority section aligns with CSC 4.8, which deals with vulnerability
   priority.  Vulnerability priority in this scenario is discussed in
   terms of the vulnerability description information priority during



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   receipt, as well as the vulnerability priority with regards to
   remedies.

   The described scenario does not address the details of applying a
   remedy based on assessment results.  As such, CSC 4.5 which deals
   with mitigations and patching, is out of scope for this work.
   Similarly, CSC 4.3 prescribes performing scans in authenticated mode
   and CSC 4.6 prescribes monitoring logs.  This scenario does not get
   into the means by which data is collected, focusing on "what" to
   collect rather than "how", and as such does not have corresponding
   sections, although the procedures described are not incompatible with
   either of these controls.

   The CSC 4 System Entity Relationship diagram directly aligns with the
   scenario described in this document with the exception of applying
   patches to endpoints.

G.1.2.  Hardware and Software Inventories

   This scenario is also aligned with, and describes a process for,
   collecting and maintaining hardware and software inventories, which
   are covered by the Center for Internet Security CSC 1 "Inventory of
   Authorized and Unauthorized Devices" and CSC 2 "Inventory of
   Authorized and Unauthorized Software."  This scenario documents a
   process that is specific to collecting and maintaining hardware and
   software data attributes for vulnerability assessment purposes, but
   the collection of the hardware attributes and software inventory
   documented in the Endpoint Data Collection section that follows can
   also be used for the purpose of implementing authorized and
   unauthorized hardware and software management processes (e.g.,
   scanning tools looking for unauthorized software).  Moreover, the
   ability to accurately identify endpoints and, to a lesser degree,
   applications is integral to effective endpoint data collection and
   vulnerability management.

   The Endpoint Data Collection section does not have coverage for the
   specific details described in CSC 1 and 2 as they are different
   processes and would be out-of-scope of this scenario, but the section
   does provide the data necessary to support the controls.

   The Endpoint Identification and Endpoint Data Collection sections
   within this scenario align with CSC 1.1 and 1.4 by identifying
   enterprise endpoints and collecting their hardware and network
   attributes.  The Endpoint Data Collection section aligns with and
   supports CSC 2.3 by defining a software inventory process and a
   method of obtaining operating system and file system attributes.  The
   rest of the items from CSC 1 and 2 deal with implementation details
   and would be out-of-scope for this document.



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Appendix H.  Continuous Vulnerability Assessment

   It is not sufficient to perform a single assessment when
   vulnerability description information is published without any
   further checking.  Doing so does not address the possibility that the
   reported vulnerability might be introduced to the enterprise
   environment after the initial assessment completes.  For example, new
   endpoints can be introduced to the environment which have old
   software or are not up-to-date with patches.  Another example is
   where unauthorized or obsolete software is installed on an existing
   endpoint by enterprise users after vulnerability description
   information and initial assessment has taken place.  Moreover,
   enterprises might not wish to, or be able to, assess all
   vulnerability description information immediately when they come in.
   Conflicts with other critical activities or limited resources might
   mean that some alerts, especially those that the enterprise deems as
   "low priority", are not used to guide enterprise assessments until
   sometime after the initial receipt.

   The scenario above describes a single assessment of endpoints.
   However, it does not make any assumptions as to when this assessment
   occurs relative to the original receipt of the vulnerability
   description data that led to this assessment.  The assessment could
   immediately follow the ingestion of the vulnerability description
   information, could be delayed, or the assessment might represent a
   reassessment of some vulnerability description information against
   which endpoints had previously been assessed.  Moreover, the scenario
   incorporates long-term storage of collected data, vulnerability
   description information, and assessment results in order to
   facilitate meaningful and ongoing reassessment.

Appendix I.  Data Attribute Table

   The following table maps all major data attributes against each major
   process where they are used.

   +--------------+------------+-------------+-------------+-----------+
   |              | vulnerabil | Endpoint Id | Endpoint Ap | Assessmen |
   |              | ity descri | entificatio | plicability | t Results |
   |              | ption data |    n and    |     and     |           |
   |              |            |   Initial   |  Assessment |           |
   |              |            |     Data    |             |           |
   |              |            |  Collection |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |  *Endpoint*  |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |  Collection  |            |      X      |      X      |           |
   |  date/time   |            |             |             |           |



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   +--------------+------------+-------------+-------------+-----------+
   |   Endpoint   |            |      X      |      X      |           |
   |     type     |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | Hardware ver |     X      |      X      |      X      |           |
   | sion/firmwar |            |             |             |           |
   |      e       |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |  Operating   |     X      |      X      |      X      |           |
   |    system    |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |  Operating   |     X      |      X      |      X      |           |
   |    system    |            |             |             |           |
   |  attributes  |            |             |             |           |
   |    (e.g.,    |            |             |             |           |
   |   version,   |            |             |             |           |
   | service pack |            |             |             |           |
   |    level,    |            |             |             |           |
   |   edition,   |            |             |             |           |
   |    etc.)     |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |  Installed   |     X      |      X      |      X      |     X     |
   |   software   |            |             |             |           |
   |     name     |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |  Installed   |     X      |      X      |      X      |     X     |
   |   software   |            |             |             |           |
   |  attributes  |            |             |             |           |
   |    (e.g.,    |            |             |             |           |
   |   version,   |            |             |             |           |
   | patch level, |            |             |             |           |
   |   install    |            |             |             |           |
   | path, etc.)  |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | Open ports/s |     X      |      X      |      X      |           |
   |   ervices    |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |  Operating   |     X      |      X      |      X      |           |
   |    system    |            |             |             |           |
   |   optional   |            |             |             |           |
   |  component   |            |             |             |           |
   |  inventory   |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |   Location   |            |      X      |             |     X     |
   +--------------+------------+-------------+-------------+-----------+
   |   Purpose    |            |      X      |             |     X     |
   +--------------+------------+-------------+-------------+-----------+
   | Criticality  |            |      X      |             |     X     |



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   +--------------+------------+-------------+-------------+-----------+
   | File system  |     X      |             |      X      |           |
   |  attributes  |            |             |             |           |
   |    (e.g.,    |            |             |             |           |
   |  versions,   |            |             |             |           |
   | size, write  |            |             |             |           |
   |    date,     |            |             |             |           |
   |   modified   |            |             |             |           |
   |    date,     |            |             |             |           |
   |  checksum,   |            |             |             |           |
   |    etc.)     |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |    Shared    |     X      |             |      X      |           |
   |  libraries   |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |    Other     |     X      |             |      X      |           |
   | software con |            |             |             |           |
   |  figuration  |            |             |             |           |
   | information  |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | *External vu |            |             |             |           |
   | lnerability  |            |             |             |           |
   | description  |            |             |             |           |
   |    data*     |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | Ingest Date  |     X      |             |      X      |           |
   +--------------+------------+-------------+-------------+-----------+
   |   Date of    |     X      |             |      X      |           |
   |   Release    |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |   Version    |     X      |             |      X      |           |
   +--------------+------------+-------------+-------------+-----------+
   |   External   |     X      |             |      X      |     X     |
   |   vuln ID    |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |   Severity   |            |             |             |     X     |
   |    Score     |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | *Assessment  |            |             |             |           |
   |   Results*   |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |   Date of    |            |             |      X      |     X     |
   |  assessment  |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | Date of data |            |      X      |      X      |     X     |
   |  collection  |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | Endpoint ide |            |      X      |      X      |     X     |



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   | ntification  |            |             |             |           |
   |    and/or    |            |             |             |           |
   |   locally    |            |             |             |           |
   | assigned ID  |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   |  Vulnerable  |     X      |      X      |      X      |     X     |
   |   software   |            |             |             |           |
   |  product(s)  |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | Endpoint vul |            |             |      X      |     X     |
   |  nerability  |            |             |             |           |
   |    status    |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | Vulnerabilit |     X      |             |             |     X     |
   |      y       |            |             |             |           |
   | description  |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+
   | Vulnerabilit |     X      |             |             |     X     |
   |      y       |            |             |             |           |
   | remediation  |            |             |             |           |
   +--------------+------------+-------------+-------------+-----------+

               Table 1: Vulnerability Assessment Attributes

Authors' Addresses

   Christopher Coffin
   The MITRE Corporation
   202 Burlington Road
   Bedford, MA  01730
   USA

   Email: ccoffin@mitre.org


   Brant Cheikes
   The MITRE Corporation
   202 Burlington Road
   Bedford, MA  01730
   USA

   Email: bcheikes@mitre.org









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   Charles Schmidt
   The MITRE Corporation
   202 Burlington Road
   Bedford, MA  01730
   USA

   Email: cmschmidt@mitre.org


   Daniel Haynes
   The MITRE Corporation
   202 Burlington Road
   Bedford, MA  01730
   USA

   Email: dhaynes@mitre.org


   Jessica Fitzgerald-McKay
   Department of Defense
   9800 Savage Road
   Ft. Meade, Maryland
   USA

   Email: jmfitz2@nsa.gov


   David Waltermire
   National Institute of Standards and Technology
   100 Bureau Drive
   Gaithersburg, Maryland  20877
   USA

   Email: david.waltermire@nist.gov

















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