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SACM Vulnerability Assessment Scenario
draft-coffin-sacm-vuln-scenario-00

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This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Authors Chris Coffin , Brant Cheikes , Charles Schmidt , Daniel Haynes , Jessica Fitzgerald-McKay , David Waltermire
Last updated 2015-10-18
Replaced by draft-ietf-sacm-vuln-scenario
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draft-coffin-sacm-vuln-scenario-00
SACM                                                           C. Coffin
Internet-Draft                                                B. Cheikes
Intended status: Informational                                C. Schmidt
Expires: April 20, 2016                                        D. Haynes
                                                   The MITRE Corporation
                                                     J. Fitzgerald-McKay
                                                   Department of Defense
                                                           D. Waltermire
                          National Institute of Standards and Technology
                                                        October 18, 2015

                 SACM Vulnerability Assessment Scenario
                   draft-coffin-sacm-vuln-scenario-00

Abstract

   This document provides a core narrative that walks through an
   automated enterprise vulnerability assessment scenario.  It is
   aligned with the SACM "Endpoint Security Posture Assessment:
   Enterprise Use Cases" [RFC7632].  It begins with an enterprise
   ingesting a vulnerability report and ends at the point of identifying
   affected endpoints.  Processes that specifically overlap between this
   scenario and RFC 7632 will be noted where applicable.  Specifically,
   the relationship between this document and the RFC 7632 use case
   building block capabilities and the usage scenarios will be covered.

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 April 20, 2016.

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Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   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.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Assumptions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Endpoint Identification and Initial (Pre-Assessment) Data
       Collection  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Identification  . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Processing Artifacts  . . . . . . . . . . . . . . . . . .   6
     3.3.  Endpoint Data Collection  . . . . . . . . . . . . . . . .   6
   4.  Vulnerability Reports . . . . . . . . . . . . . . . . . . . .   8
   5.  Endpoint Applicability and Assessment . . . . . . . . . . . .   9
     5.1.  Applicability . . . . . . . . . . . . . . . . . . . . . .   9
     5.2.  Secondary Assessment  . . . . . . . . . . . . . . . . . .   9
   6.  Assessment Reports  . . . . . . . . . . . . . . . . . . . . .  11
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   9.  Informative References  . . . . . . . . . . . . . . . . . . .  12
   Appendix A.  Continuous Vulnerability Assessment  . . . . . . . .  12
   Appendix B.  Priority . . . . . . . . . . . . . . . . . . . . . .  13
   Appendix C.  Data Attribute Table and Definitions . . . . . . . .  14
     C.1.  Table . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     C.2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .  16
   Appendix D.  Alignment with Other Existing Works  . . . . . . . .  18
     D.1.  Critical Security Controls  . . . . . . . . . . . . . . .  18
       D.1.1.  Continuous Vulnerability Assessment . . . . . . . . .  18
       D.1.2.  Hardware and Software Inventories . . . . . . . . . .  19
   Appendix E.  SACM Usage Scenarios . . . . . . . . . . . . . . . .  20
   Appendix F.  SACM Requirements and Charter - Future Work  . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

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1.  Scope

   The purpose of this document is to describe a detailed scenario for
   vulnerability assessment, and identify aspects of this scenario that
   could be used in the development of an information model.  This
   includes classes of data, major roles, and a high-level description
   of role interactions.  Additionally, this scenario can also inform
   engineering work on protocol and data model development.  The focus
   of the document is entirely intra-organizational and covers
   enterprise handling of vulnerability reports.  The document does not
   attempt to cover the security disclosure itself and any prior
   activities of the security researcher or discloser, nor does it
   attempt to cover the specific activities of the vendor whose software
   is the focus of a vulnerability report.

   For the purposes of this document, the term "vulnerability report" is
   intended to mean: "A publication intended to alert enterprise IT
   resources to the existence of a flaw or flaws in software, hardware,
   and/or firmware, which could potentially have an impact on enterprise
   functionality and/or security."  For the purpose of this scenario,
   such a report also includes information that can be used to determine
   (to some level of accuracy, although possibly not conclusively)
   whether or not the flaw is present within an enterprise, when
   compared to information about the state of the enterprise's
   endpoints.

   This document makes no attempt to provide a definition of a
   normalized data format for vulnerability reports.  Also, it does not
   attempt to define procedures by which a vulnerability discoverer
   coordinates the release of a report with other parties.

2.  Assumptions

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

   o  The document begins with the assumption that the enterprise has
      received a vulnerability report, and that the report data has
      already been processed into a format that the enterprise's
      security software tools can understand and use.  In particular,
      this document:

      *  Does not discuss how the enterprise identifies a potentially
         relevant vulnerability report.

      *  Does not discuss how the enterprise collects that report.

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      *  Does not discuss how the enterprise assesses the authenticity
         of the report.

      *  Does not discuss parsing of the report into a usable format.

   o  The document assumes that the enterprise has a means of
      identifying enterprise endpoints.  This could mean identifying
      endpoints as they join the network, actively scanning for
      connected endpoints, passive scanning of network traffic to
      identify connected endpoints, or some other method of accounting
      for the presence of all endpoints in the enterprise.

   o  The document assumes that the enterprise has a means of extracting
      relevant infomation about enterprise endpoints.  Moreover, this
      extracted information is expressed in a format that is compatible
      with the information extracted from the vulnerability report.  The
      document:

      *  Does not specify how relevant information is identified.

      *  Does not specify the mechanics of how relevant information is
         extracted from the data sources (such as the endpoint itself).

      *  Does not specify how extracted endpoint information and
         vulnerability alert information are normalized to be
         compatible.

      Note that having a means of extracting relevant information about
      enterprise endpoints is within the scope of the SACM Endpoint
      Security Posture Assessment process.  In the case of this
      document, this sub-process is assumed to be existent.

   o  The document assumes that all information described in the steps
      below is available in the vulnerability report and serves as the
      basis of this assessment.  Likewise, the document assumes that the
      enterprise can provide all relevant information about any endpoint
      needed to perform the described analysis.  The authors recognize
      that this will not always be the case, but these assumptions are
      taken in order to show the breadth of data utilization in this
      scenario.  Less complete information may require variations to the
      described steps.

   o  The document assumes that the enterprise has a policy by which
      assessment of endpoints based on vulnerability reports are
      prioritized.  The document:

      *  Does not specify how prioritization occurs.

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      *  Does not specify how prioritization impacts assessment
         behaviors.

   o  The document assumes that the enterprise has a mechanism for long-
      term storage of vulnerability reports and endpoint assessment
      results.

   o  This document assumes that the enterprise has a procedure for
      reassessment of endpoints at some point after initial assessment.
      The document:

      *  Does not specify how a reassessment would impact individual
         assessment behaviors.  (I.e., it is agnostic as to whether the
         assessment procedure is the same regardless of whether this is
         the first or a subsequent assessment for a given vulnerability
         report.)

      *  Does not provide guidance or specifics on reassessment
         intervals.

3.  Endpoint Identification and Initial (Pre-Assessment) Data Collection

   The first step in this scenario involves identifying endpoints and
   collecting basic system information from them.  This occurs prior to
   the receipt of any specific vulnerability report and is part of the
   regular, ongoing monitoring of endpoints within an enterprise.  This
   process is not meant to report on, or gather data for any specific
   vulnerabilities.  The information gathered during this step could be
   applied in many enterprise automation efforts.  Specifically, in
   addition to vulnerability management, it could be used by
   configuration and license management tasks.  All of the information
   collected during this step is stored in a central location such as a
   CMDB.

   This activity involves the following sub-steps:

3.1.  Identification

   Prior to any other steps, the identification of endpoints must occur.
   This involves locating (at least virtually) and distinguishing
   between endpoints on the network in a way that allows each endpoint
   to be recognized in future interactions and selected for specific
   treatment.  This not only allows later steps to determine the scope
   of what systems need to be assessed, but also allows for the unique
   identification of each endpoint.  Unique endpoint IDs are used to
   allow for systems to be tracked over time and also allow for proper
   counts of assets during inventories and other similar collections.
   Endpoint identity can be established by collecting certain system

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   properties that allow persistent tracking of the endpoints.  Examples
   include, but are not limited to, IP address, MAC address, FQDNs, pre-
   provisioned identifiers such as GUIDs or copies of serial numbers,
   certificates, hardware identity values, or similar.

   This sub-step aligns with the Endpoint Discovery, Endpoint
   Characterization (automated collection data only), 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.

3.2.  Processing Artifacts

   Processing artifacts, such as the date and time the collection was
   performed, should be collected and stored.  This timestamp is
   extremely important when performing later assessments, as it is
   needed for data freshness computations.  The organization may develop
   rules for stale data and when a new data collection is required.
   This metadata is also helpful in correlating information across
   multiple data collections.  This includes correlating both pre-
   assessment data and secondary assessment data (sections 4.3 Endpoint
   Data Collection and 6.2 Secondary Assessment).

3.3.  Endpoint Data Collection

   The enterprise should perform ongoing collection of basic endpoint
   information such as operating system and version information, and an
   installed software inventory.  This information is collected for
   general system monitoring as well as its potential use in activities
   such as vulnerability assessment.

   Some basic information to collect from endpoints in this pre-
   vulnerability report and pre-assessment process could include:

   o  Endpoint type - e.g., standard computer, printer, router, mobile
      device, tablet, etc.

   o  Hardware version/firmware

   o  Operating system - Windows, Linux, OSX, Android

   o  Operating system attributes - e.g., version, patch level, service
      pack level, internationalized or localized version, etc.

   o  Installed software inventory - important for later assessments.
      Would include the software names and versions (and possibly other
      high-level attributes).  Could be used to quickly determine
      endpoint applicability in later vulnerability reports.

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   o  Open ports/running services

   o  Operating system optional component inventory - some OS' have
      optional components that can be installed which may not show up as
      separate pieces of software (e.g., web and ftp servers, demo web
      pages, shared libraries, etc.).  Note that this could also occur
      within third-party applications as well.

   In addition to the above, the possibility should be left open for
   enterprises to define their own custom queries to gather enterprise-
   specific system attributes that are deemed of interest to regular
   enterprise operations.

   Human-assigned endpoint attributes are yet another type of data item
   that could be collected here.  This would include any attributes that
   cannot be collected programmatically.  The attributes could be
   manually entered into a CMDB by a human after the initial data
   collection occurs.  The attributes could help with system
   categorization and may have influence on later prioritizations.  The
   human-assigned attributes could include:

   o  Location - physical location, department, room, etc.

   o  Role - The function that the endpoint serves within the enterprise
      (end user system, database server, public web server, etc.)

   o  Criticality - enterprise defined rating (possibly a score) that
      helps determine the criticality of the endpoint.  If this endpoint
      is attacked or lost, what is the impact to the overall enterprise?

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

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4.  Vulnerability Reports

   The next step in the Vulnerability Assessment scenario begins after a
   vulnerability report has been received and processed into a form that
   can be used in the assessment of the enterprise.  As a part of the
   enterprise process for managing vulnerability reports, the enterprise
   should store all received and processed vulnerability reports in a
   CMDB.  These stored vulnerability reports can be used and compared
   with later vulnerability reports for the purpose of duplicate
   detection and in some cases guidance on how to handle similar issues.

   All vulnerability reports should be assigned an internal tracking ID
   by the enterprise as a first step.  Incoming vulnerability reports
   might not have a global identifier when they are received, and might
   never have one assigned.

   High-level vulnerability report metadata to store would include:

   o  Ingest Date - the date that the report was received by the
      enterprise.

   o  Date of Report Release (i.e., publication or disclosure date) -
      Some older reports may be ingested long after publication.  This
      can be useful when reviewing historical enterprise information to
      (potentially) identify the period when a particular endpoint was
      first vulnerable.  Sometimes this information will help to
      differentiate between similar vulnerability reports.

   o  Report Version - the version or iteration of the report according
      to the report author, if applicable.

   o  External Report ID(s) (if applicable) - any external or third-
      party IDs assigned to the report should be tracked.  There could
      be multiple IDs in some cases (e.g., vendor bug id, global ID,
      discoverer's local ID, third-party vulnerability database ID,
      etc.).

   o  Severity Score (if available) - these may be useful for later
      mitigation prioritization.

   In addition to the described metadata, all vulnerability reports
   would be stored with the information extracted from them that is to
   be used in the applicability and assessment process.

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

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5.  Endpoint Applicability and Assessment

   When a new vulnerability report is received by the enterprise,
   applicable enterprise endpoints must be identified and assessed.
   Endpoints are first examined using pre-assessment data.  If this is
   not sufficient to determine endpoint applicability, a secondary data
   collection for additional data and attributes may be performed to
   determine status with regard to the vulnerability report.

5.1.  Applicability

   The applicability of an endpoint and its vulnerability status can, in
   many cases, be determined entirely by the existence of a particular
   version of installed software on the endpoint.  This data would
   already have been collected in the pre-assessment data collection.
   If the applicability and vulnerability status of an endpoint can be
   determined entirely by the pre-collected data attribute set, no
   further data collection is required.

   Other cases may require specific data (i.e., file system attributes,
   specific configuration parameters, etc.) to be collected for the
   assessment of a particular vulnerability report.  In these cases, a
   secondary, targeted vulnerability assessment is required.
   Administrators may want to evaluate applicability to the
   vulnerability report iteratively.  Specifically, the process would
   compare against pre-collected data first (easy to do and the data is
   stored in a CMDB), and then if needed, query endpoints that are not
   already excluded from applicability for additional required data.
   (I.e., A "fast-fail" model).  To do this, the criteria for
   determining applicability must be separable, so that some conclusions
   can be drawn based on the possession of partial data.

   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.

5.2.  Secondary Assessment

   If the applicability and vulnerability status of an endpoint cannot
   be determined by the pre-assessment data collection, a secondary and
   targeted assessment of the endpoint will be required.  A secondary
   assessment may also be required in the case that data on-hand (either
   from pre-assessment or from prior secondary assessments) is stale or
   out-of-date.

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   The following data types and attributes are examples of what might be
   required in the case of a secondary and targeted assessment:

   o  Specific files and attributes - i.e., file name, versions, size,
      write date, modified date, checksum, etc.  Some vulnerabilities
      may only be distinguishable through the presence or absence of
      specific files.

   o  Shared libraries - Some vulnerabilities will affect many products
      across multiple vendors.  In these cases the vulnerability may
      apply to a shared library.  Under these circumstances, product
      versions may be less helpful than looking for the presence of one
      or more specific files and their attributes.

   o  Other software configuration information (if applicable) - such as
      Microsoft Windows registry queries, text configuration files and
      their parameters, and the installation paths.  Sometimes
      vulnerabilities only affect certain software configurations and in
      some cases these are not the default configurations.  Certain
      configuration attributes can be used to determine the current
      configuration state.

   Note that the secondary assessment described here does not need to be
   a pull assessment that is initiated by the server.  The secondary
   assessment could also be part of a push to the server when the
   endpoint detects a change to a vulnerability assessment baseline.

   This sub-step aligns with the Data Publication building block
   capability because this section details storage of endpoint
   attributes within an enterprise CMDB.  The sub-step also aligns with
   the Collection Guidance Acquisition building block capability since
   the vulnerability report (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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6.  Assessment Reports

   An assessment report presents the results of an assessment, along
   with sufficient context so a human or machine can make the
   appropriate response.  This context might include a description of
   the issue provided by the vulnerability report, the endpoint
   attributes that indicate applicability, or other information needed
   to respond to the report determination.  Data in this step is stored
   for auditing and forensic purposes.

   The following details are important to track in an assessment report.
   Note that information may be "included" by providing pointers to
   other records stored in a CMDB.

   o  Date of assessment - The date that the assessment was performed.
      To understand when the data was compared against the vulnerability
      report and what conclusions were drawn.

   o  Data collection/attribute age - The age of the data used in the
      assessment to make the endpoint status determination.

   o  Endpoint ID - The endpoint itself must be identified for tracking
      results over time.

   o  Vulnerability report ID - Allows linkage to the correct
      vulnerability report.  The ID could be internally or externally
      defined (or both).

   o  Vulnerable software product(s) - Identifies the software products
      on the endpoint that resulted in the endpoint being declared
      applicable.  Since some vulnerability reports identify
      vulnerabilities in multiple products, this will help identify the
      specific product (or products) found to be vulnerable in the
      endpoint assessment.

   o  Endpoint vulnerability status - The endpoint status based on the
      vulnerability report.  Does the vulnerability exist on the
      endpoint?

   o  Vulnerability description - Not needed for automated assessment
      but probably should be included for human review.  The reason for
      inclusion is to support the human user understanding of the
      vulnerability assessment report within the application front-end
      or interface.

   This step aligns with the Data Publication and Data Retrieval
   building block capabilities because this section details storage of

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   vulnerability assessment reports within an enterprise CMDB and later
   retrieval of the same.

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] . It is for informational purposes only.  As a
   result, there are no specific security considerations.

9.  Informative References

   [charter-ietf-sacm-01]
              Security Automation and Continuous Monitoring, "Charter,
              Version 1.0", July 2013.

   [critical-controls]
              Council on CyberSecurity, "Critical Security Controls,
              Version 5.1".

   [I-D.ietf-sacm-requirements]
              Cam-Winget, N. and L. Lorenzin, "Secure Automation and
              Continuous Monitoring (SACM) Requirements", draft-ietf-
              sacm-requirements-10 (work in progress), October 2015.

   [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.  Continuous Vulnerability Assessment

   It is not sufficient to perform a single assessment when a
   vulnerability report 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
   such an assessment completes.  For example, new endpoints can be
   introduced to the environment which have old software or are not up-
   to-date with patches.  This is especially true of BYOD environments.
   Another example is where unauthorized or obsolete software is
   installed on an existing endpoint by enterprise users after a
   vulnerability report and initial assessment has taken place.
   Moreover, enterprises might not wish to, or be able to, assess all

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   vulnerability reports 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 report
   that led to this assessment.  The assessment could immediately follow
   ingest of the report, could be delayed, or the assessment might
   represent a reassessment of some report against which endpoints had
   previously been assessed.  Moreover, the scenario incorporates long-
   term storage of collected data, vulnerability reports, and assessment
   results in order to facilitate meaningful ongoing reassessment.

Appendix B.  Priority

   Priorities associated with both the reports 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 report scenario as they
   separable issues with their own sets of requirements.

   Priority in regard to vulnerability reports, can be viewed in a
   couple of different ways within an enterprise.  The assessment
   prioritization involves prioritization of the vulnerability report
   assessment process.  This determines which vulnerability reports are
   assessed, and in what order they are 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
   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 reports 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

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   prioritize based only on what they know about their enterprise and
   the description provided in the vulnerability report.

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

   o  Enterprise-defined role 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.

Appendix C.  Data Attribute Table and Definitions

C.1.  Table

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

   +--------------------+--------+------------+------------+-----------+
   |                    | Vuln.  |   Init.    | Assessment | Reporting |
   |                    | Report | Collection |            |           |
   +--------------------+--------+------------+------------+-----------+
   |     *Endpoint*     |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |     Collection     |        |     X      |     X      |           |
   |     date/time      |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |   Endpoint type    |        |     X      |     X      |           |
   +--------------------+--------+------------+------------+-----------+
   |      Hardware      |   X    |     X      |     X      |           |
   |  version/firmware  |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |  Operating system  |   X    |     X      |     X      |           |
   +--------------------+--------+------------+------------+-----------+
   |  Operating system  |   X    |     X      |     X      |           |
   | attributes (e.g.,  |        |            |            |           |
   |  version, service  |        |            |            |           |
   |    pack level,     |        |            |            |           |
   |   edition, etc.)   |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   | Installed software |   X    |     X      |     X      |     X     |
   |        name        |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   | Installed software |   X    |     X      |     X      |     X     |
   | attributes (e.g.,  |        |            |            |           |
   |   version, patch   |        |            |            |           |

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   |   level, install   |        |            |            |           |
   |    path, etc.)     |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |        Open        |   X    |     X      |     X      |           |
   |   ports/services   |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |  Operating system  |   X    |     X      |     X      |           |
   | optional component |        |            |            |           |
   |     inventory      |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |      Location      |        |     X      |            |     X     |
   +--------------------+--------+------------+------------+-----------+
   |        Role        |        |     X      |            |     X     |
   +--------------------+--------+------------+------------+-----------+
   |    Criticality     |        |     X      |            |     X     |
   +--------------------+--------+------------+------------+-----------+
   |    File system     |   X    |            |     X      |           |
   | attributes (e.g.,  |        |            |            |           |
   |  versions, size,   |        |            |            |           |
   |    write date,     |        |            |            |           |
   |   modified date,   |        |            |            |           |
   |  checksum, etc.)   |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |  Shared libraries  |   X    |            |     X      |           |
   +--------------------+--------+------------+------------+-----------+
   |   Other software   |   X    |            |     X      |           |
   |   configuration    |        |            |            |           |
   |    information     |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |     *External      |        |            |            |           |
   |   Vulnerability    |        |            |            |           |
   |      Report*       |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |    Ingest Date     |   X    |            |     X      |           |
   +--------------------+--------+------------+------------+-----------+
   |  Date of Release   |   X    |            |     X      |           |
   +--------------------+--------+------------+------------+-----------+
   |   Report Version   |   X    |            |     X      |           |
   +--------------------+--------+------------+------------+-----------+
   | External Report ID |   X    |            |     X      |     X     |
   +--------------------+--------+------------+------------+-----------+
   |   Severity Score   |        |            |            |     X     |
   +--------------------+--------+------------+------------+-----------+
   |    *Assessment     |        |            |            |           |
   |      Report*       |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   | Date of assessment |        |            |     X      |     X     |
   +--------------------+--------+------------+------------+-----------+

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   |    Date of data    |        |     X      |     X      |     X     |
   |     collection     |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |      Endpoint      |        |     X      |     X      |     X     |
   |   identification   |        |            |            |           |
   |   and/or locally   |        |            |            |           |
   |    assigned ID     |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |     Vulnerable     |   X    |     X      |     X      |     X     |
   |      software      |        |            |            |           |
   |     product(s)     |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |      Endpoint      |        |            |     X      |     X     |
   |   vulnerability    |        |            |            |           |
   |       status       |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+
   |   Vulnerability    |   X    |            |            |     X     |
   |    description     |        |            |            |           |
   +--------------------+--------+------------+------------+-----------+

               Table 1: Vulnerability Assessment Attributes

C.2.  Definitions

   Endpoint

   o  Collection date/time - the date and time of data collection

   o  Endpoint type - the device type of the endpoint (e.g., standard
      computer, printer, router, mobile device, tablet, etc.)

   o  Hardware version/firmware - the hardware or firmware version (if
      applicable)

   o  Operating system - Operating system name

   o  Operating system attributes - Operating system high-level
      attributes (e.g., version, service pack level, edition, etc.).
      Would not include configuration details.

   o  Installed software name - List of all installed software packages
      (i.e., software inventory).  May or may not include software
      installed by the operating system.

   o  Installed software attributes - Software high-level attributes
      (e.g., version, patch level, install path, etc.).  Would not
      include configuration details.

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   o  Open ports/services - Listening network ports (TCP and UDP) and
      running services

   o  Operating system optional component inventory - Operating system
      specific components and software (when NOT already included in the
      general software inventory)

   o  Location - The physical location of an enterprise endpoint
      (department, room, etc.)

   o  Role - The function that the endpoint serves within the enterprise
      (e.g., end user system, database server, public web server, etc.)

   o  Criticality - An enterprise-defined rating (possibly a score) that
      helps determine the criticality of the endpoint.  If this endpoint
      is attacked or lost, what is the impact to the overall enterprise?

   o  File system attributes - Attributes that describe the state of a
      file or directory (e.g., versions, size, write date, modified
      date, checksum, etc.)

   o  Shared libraries - libraries that can be used by and installed
      with many different software applications.  A shared library
      vulnerability could affect multiple software applications in the
      same way.

   o  Other software configuration information - operating system or
      software application configuration attributes that go beyond that
      basic information already captured (Microsoft Windows registry,
      text configuration files and their parameters, and the
      installation paths.)

   External Vulnerability Report

   o  Ingest Date - the date that the report was received by the
      enterprise.

   o  Date of Release - publication or disclosure date of the
      vulnerability report

   o  Report Version - the version or iteration of the report according
      to the report author, if applicable.

   o  External Report ID - external or third-party IDs assigned to the
      report.  Could be multiple IDs in some cases (e.g., vendor bug id,
      global ID, discoverer's local ID, third-party vulnerability
      database ID, etc.).

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   o  Severity Score - the severity of the report according to the
      report author, if applicable.

   Assessment Report

   o  Date of assessment - The date that the assessment was performed
      against an endpoint.

   o  Date of data collection - The age of the data used in the
      assessment to make the endpoint status determination.

   o  Endpoint identification and/or locally assigned ID - The ID
      assigned to the enterprise endpoint.  Must be assigned for
      tracking results over time.

   o  Vulnerable software product(s) - The vulnerable software products
      identified as being installed on the endpoint.

   o  Endpoint vulnerability status - Overall vulnerability status of
      the enterprise endpoint (i.e., Pass or Fail)

   o  Vulnerability description - A human-consumable description of a
      vulnerability.  Supports the human user understanding of the
      vulnerability assessment report within an application front-end or
      user interface.

Appendix D.  Alignment with Other Existing Works

D.1.  Critical Security Controls

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

D.1.1.  Continuous Vulnerability Assessment

   "CSC 4: Continuous Vulnerability Assessment and Remediation," which
   is described by the Council on CyberSecurity 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

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   this document is intended to be executed on a continuous basis, and
   the priorities of both vulnerability reports 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 reports as described in CSC 4-4.

   Both CSC 4-2 and 4-7 are made possible by writing information to a
   CMDB 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 4-10, which deals with vulnerability
   priority.  Vulnerability priority in this scenario is discussed in
   terms of the vulnerability report priority during 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, 4-8, and 4-9,
   which all deal with mitigations and patching, are 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 and numbered steps
   directly align with the scenario described in this document with the
   exception of step 7 (patch response).  Steps 1 -6 in CSC 4 describe
   the overall process for vulnerability management starting with
   obtaining the vulnerability report from the source in Step 1, to
   producing an assessment report in step 6.

D.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 Council on CyberSecurity 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

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   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 and 2-4 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.

   CSC 2-9 describes the use of a software ID tag in XML format.  SWID
   tags (https://en.wikipedia.org/wiki/ISO/IEC_19770) would also be a
   possible implementation for the Endpoint Data Collection section
   described in this scenario.

Appendix E.  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
      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

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      align almost exactly with the scenario described in this document.
      Instead of collecting automatable security configuration
      checklists, the enterprise would collect automatable vulnerability
      reports 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 a vulnerability report 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 does describe vulnerability assessment in particular, and
      aligns exactly with the scenario described in this document.  The
      endpoint assets are identified and associated data is published in
      a CMDB.  Vulnerability reports are collected and saved in a CMDB
      as they are released.  The reports are queued for later
      assessment, then the results and resulting vulnerability reports
      are stored after assessment.  The only real difference in this
      SACM usage scenario is that of 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.

Appendix F.  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

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   [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 result data set should
      include.  In the case of vulnerability assessment reports, 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 the
      reporting of results.  The concern here is with vulnerability
      reporting, 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, functions, 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.

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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