Network Working Group A. Dulaunoy Internet-Draft A. Iklody Intended status: Informational CIRCL Expires: June 2, 2018 November 29, 2017 MISP taxonomy format draft-dulaunoy-misp-taxonomy-format-04 Abstract This document describes the MISP taxonomy format which describes a simple JSON format to represent machine tags (also called triple tags) vocabularies. A public directory of common vocabularies MISP taxonomies is available and relies on the MISP taxonomy format. MISP taxonomies are used to classify cyber security events, threats or indicators. 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 https://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 June 2, 2018. Copyright Notice Copyright (c) 2017 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 (https://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 Dulaunoy & Iklody Expires June 2, 2018 [Page 1] Internet-Draft MISP taxonomy format November 2017 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions and Terminology . . . . . . . . . . . . . . . 3 2. Format . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. predicates . . . . . . . . . . . . . . . . . . . . . . . 4 2.3. values . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.4. optional fields . . . . . . . . . . . . . . . . . . . . . 4 2.4.1. colour . . . . . . . . . . . . . . . . . . . . . . . 4 2.4.2. description . . . . . . . . . . . . . . . . . . . . . 5 2.4.3. numerical_value . . . . . . . . . . . . . . . . . . . 5 3. Directory . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Sample Manifest . . . . . . . . . . . . . . . . . . . . . 7 4. Sample Taxonomy in MISP taxonomy format . . . . . . . . . . . 7 4.1. Admiralty Scale Taxonomy . . . . . . . . . . . . . . . . 7 4.2. Open Source Intelligence - Classification . . . . . . . . 9 5. JSON Schema . . . . . . . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 7.1. Normative References . . . . . . . . . . . . . . . . . . 15 7.2. Informative References . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 1. Introduction Sharing threat information became a fundamental requirements on the Internet, security and intelligence community at large. Threat information can include indicators of compromise, malicious file indicators, financial fraud indicators or even detailed information about a threat actor. While sharing such indicators or information, classification plays an important role to ensure adequate distribution, understanding, validation or action of the shared information. MISP taxonomies is a public repository of known vocabularies that can be used in threat information sharing. Machine tags were introduced in 2007 [machine-tags] to allow users to be more precise when tagging their pictures with geolocation. So a machine tag is a tag which uses a special syntax to provide more information to users and machines. Machine tags are also known as triple tags due to their format. In the MISP taxonomy context, machine tags help analysts to classify their cybersecurity events, indicators or threats. MISP taxonomies can be used for classification, filtering, triggering actions or Dulaunoy & Iklody Expires June 2, 2018 [Page 2] Internet-Draft MISP taxonomy format November 2017 visualisation depending on their use in threat intelligence platforms such as MISP [MISP-P]. 1.1. Conventions and Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2. Format A machine tag is composed of a namespace (MUST), a predicate (MUST) and an optional value (OPTIONAL). Machine tags are represented as a string. Below listed are a set of sample machine tags for different namespaces such as tlp, admiralty- scale and osint. tlp:amber admiralty-scale:information-credibility="1" osint:source-type="blog-post" The MISP taxonomy format describes how to define a machine tag namespace in a parseable format. The objective is to provide a simple format to describe machine tag (aka triple tag) vocabularies. 2.1. Overview The MISP taxonomy format uses the JSON [RFC4627] format. Each namespace is represented as a JSON object with meta information including the following fields: namespace, description, version, type. namespace defines the overall namespace of the machine tag. The namespace is represented as a string and MUST be present. The description is represented as a string and MUST be present. A version is represented as a decimal and MUST be present. A type defines where a specific taxonomy is applicable and a type can be applicable at event, user or org level. The type is represented as an array containing one or more type and SHOULD be present. If a type is not mentioned, by default, the taxonomy is applicable at event level only. An exclusive boolean property MAY be present and defines at namespace level if the predicates are mutually exclusive. predicates defines all the predicates available in the namespace defined. predicates is represented as an array of JSON objects. predicates MUST be present and MUST at least content one element. Dulaunoy & Iklody Expires June 2, 2018 [Page 3] Internet-Draft MISP taxonomy format November 2017 values defines all the values for each predicate in the namespace defined. values SHOULD be present. 2.2. predicates The predicates array contains one or more JSON objects which lists all the possible predicates. The JSON object contains two fields: value and expanded. value MUST be present. expanded SHOULD be present. value is represented as a string and describes the predicate value. The predicate value MUST not contain spaces or colons. expanded is represented as a string and describes the human-readable version of the predicate value. An exclusive property MAY be present and defines at namespace level if the values are mutually exclusive. 2.3. values The values array contain one or more JSON objects which lists all the possible values of a predicate. The JSON object contains two fields: predicate and entry. predicate is represented as a string and describes the predicate value. entry is an array with one or more JSON objects. The JSON object contains two fields: value and expanded. value MUST be present. expanded SHOULD be present. value is represented as a string and describes the machine parsable value. expanded is represented as a string and describes the human-readable version of the value. 2.4. optional fields 2.4.1. colour colour fields MAY be used at predicates or values level to set a specify colour that MAY be used by the implementation. The colour field is described as an RGB colour fill in hexadecimal representation. Example use of the colour field in the Traffic Light Protocol (TLP): Dulaunoy & Iklody Expires June 2, 2018 [Page 4] Internet-Draft MISP taxonomy format November 2017 "predicates": [ { "colour": "#CC0033", "expanded": "(TLP:RED) Information exclusively and directly given to (a group of) individual recipients. Sharing outside is not legitimate.", "value": "red" }, { "colour": "#FFC000", "expanded": "(TLP:AMBER) Information exclusively given to an organization; sharing limited within the organization to be effectively acted upon.", "value": "amber" }...] 2.4.2. description description fields MAY be used at predicates or values level to add a descriptive and human-readable information about the specific predicate or value. The field is represented as a string. Implementations MAY use the description field to improve more contextual information. The description at the namespace level is a MUST as described above. 2.4.3. numerical_value numerical_value fields MAY be used at a predicate or value level to add a machine-readable numeric value to a specific predicate or value. The field is represented as a JSON number. Implementations SHOULD use the decimal value provided to support scoring or filtering. Example use of the numerical_value in the MISP confidence level: Dulaunoy & Iklody Expires June 2, 2018 [Page 5] Internet-Draft MISP taxonomy format November 2017 { "predicate": "confidence-level", "entry": [ { "expanded": "Completely confident", "value": "completely-confident", "numerical_value": 100 }, { "expanded": "Usually confident", "value": "usually-confident", "numerical_value": 75 }, { "expanded": "Fairly confident", "value": "fairly-confident", "numerical_value": 50 }, { "expanded": "Rarely confident", "value": "rarely-confident", "numerical_value": 25 }, { "expanded": "Unconfident", "value": "unconfident", "numerical_value": 0 }, { "expanded": "Confidence cannot be evaluated", "value": "confidence-cannot-be-evalued" } ] } 3. Directory The MISP taxonomies directory is publicly available [MISP-T] in a git repository. The repository contains a directory per namespace then a file machinetag.json which contains the taxonomy as described in the format above. In the root of the repository, a MANIFEST.json exists containing a list of all the taxonomies. The MANIFEST.json file is composed of an JSON object with metadata like version, license, description, url and path. A taxonomies array describes the taxonomy available with the description, name and version field. Dulaunoy & Iklody Expires June 2, 2018 [Page 6] Internet-Draft MISP taxonomy format November 2017 3.1. Sample Manifest { "version": "20161009", "license": "CC-0", "description": "Manifest file of MISP taxonomies available.", "url": "https://raw.githubusercontent.com/MISP/misp-taxonomies/master/", "path": "machinetag.json", "taxonomies": [ { "description": "The Admiralty Scale (also called the NATO System) is used to rank the reliability of a source and the credibility of an information.", "name": "admiralty-scale", "version": 1 }, { "description": "Open Source Intelligence - Classification.", "name": "osint", "version": 2 }] } 4. Sample Taxonomy in MISP taxonomy format 4.1. Admiralty Scale Taxonomy "namespace": "admiralty-scale", "description": "The Admiralty Scale (also called the NATO System) is used to rank the reliability of a source and the credibility of an information.", "version": 1, "predicates": [ { "value": "source-reliability", "expanded": "Source Reliability" }, { "value": "information-credibility", "expanded": "Information Credibility" } ], "values": [ { "predicate": "source-reliability", "entry": [ { Dulaunoy & Iklody Expires June 2, 2018 [Page 7] Internet-Draft MISP taxonomy format November 2017 "value": "a", "expanded": "Completely reliable" }, { "value": "b", "expanded": "Usually reliable" }, { "value": "c", "expanded": "Fairly reliable" }, { "value": "d", "expanded": "Not usually reliable" }, { "value": "e", "expanded": "Unreliable" }, { "value": "f", "expanded": "Reliability cannot be judged" } ] }, { "predicate": "information-credibility", "entry": [ { "value": "1", "expanded": "Confirmed by other sources" }, { "value": "2", "expanded": "Probably true" }, { "value": "3", "expanded": "Possibly true" }, { "value": "4", "expanded": "Doubtful" }, { "value": "5", "expanded": "Improbable" }, Dulaunoy & Iklody Expires June 2, 2018 [Page 8] Internet-Draft MISP taxonomy format November 2017 { "value": "6", "expanded": "Truth cannot be judged" } ] } ] } 4.2. Open Source Intelligence - Classification { "values": [ { "entry": [ { "expanded": "Blog post", "value": "blog-post" }, { "expanded": "Technical or analysis report", "value": "technical-report" }, { "expanded": "News report", "value": "news-report" }, { "expanded": "Pastie-like website", "value": "pastie-website" }, { "expanded": "Electronic forum", "value": "electronic-forum" }, { "expanded": "Mailing-list", "value": "mailing-list" }, { "expanded": "Block or Filter List", "value": "block-or-filter-list" }, { "expanded": "Expansion", "value": "expansion" } ], Dulaunoy & Iklody Expires June 2, 2018 [Page 9] Internet-Draft MISP taxonomy format November 2017 "predicate": "source-type" }, { "predicate": "lifetime", "entry": [ { "value": "perpetual", "expanded": "Perpetual", "description": "Information available publicly on long-term" }, { "value": "ephemeral", "expanded": "Ephemeral", "description": "Information available publicly on short-term" } ] }, { "predicate": "certainty", "entry": [ { "numerical_value": 100, "value": "100", "expanded": "100% Certainty", "description": "100% Certainty" }, { "numerical_value": 93, "value": "93", "expanded": "93% Almost certain", "description": "93% Almost certain" }, { "numerical_value": 75, "value": "75", "expanded": "75% Probable", "description": "75% Probable" }, { "numerical_value": 50, "value": "50", "expanded": "50% Chances about even", "description": "50% Chances about even" }, { "numerical_value": 30, "value": "30", "expanded": "30% Probably not", Dulaunoy & Iklody Expires June 2, 2018 [Page 10] Internet-Draft MISP taxonomy format November 2017 "description": "30% Probably not" }, { "numerical_value": 7, "value": "7", "expanded": "7% Almost certainly not", "description": "7% Almost certainly not" }, { "numerical_value": 0, "value": "0", "expanded": "0% Impossibility", "description": "0% Impossibility" } ] } ], "namespace": "osint", "description": "Open Source Intelligence - Classification", "version": 3, "predicates": [ { "value": "source-type", "expanded": "Source Type" }, { "value": "lifetime", "expanded": "Lifetime of the information as Open Source Intelligence" }, { "value": "certainty", "expanded": "Certainty of the elements mentioned in this Open Source Intelligence" } ] } 5. JSON Schema The JSON Schema [JSON-SCHEMA] below defines the structure of the MISP taxonomy document as literally described before. The JSON Schema is used validating a MISP taxonomy. The validation is a _MUST_ if the taxonomy is included in the MISP taxonomies directory. { "$schema": "http://json-schema.org/schema#", Dulaunoy & Iklody Expires June 2, 2018 [Page 11] Internet-Draft MISP taxonomy format November 2017 "title": "Validator for misp-taxonomies", "id": "https://www.github.com/MISP/misp-taxonomies/schema.json", "defs": { "entry": { "type": "array", "uniqueItems": true, "items": { "type": "object", "additionalProperties": false, "properties": { "numerical_value": { "type": "number" }, "expanded": { "type": "string" }, "description": { "type": "string" }, "colour": { "type": "string" }, "value": { "type": "string" }, "required": [ "value" ] } } }, "values": { "type": "array", "uniqueItems": true, "items": { "type": "object", "additionalProperties": false, "properties": { "entry": { "$ref": "#/defs/entry" }, "predicate": { "type": "string" } }, "required": [ "predicate" ] Dulaunoy & Iklody Expires June 2, 2018 [Page 12] Internet-Draft MISP taxonomy format November 2017 } }, "predicates": { "type": "array", "uniqueItems": true, "items": { "type": "object", "additionalProperties": false, "properties": { "numerical_value": { "type": "number" }, "colour": { "type": "string" }, "description": { "type": "string" }, "expanded": { "type": "string" }, "value": { "type": "string" }, "exclusive": { "type": "boolean" }, "required": [ "value" ] } } } }, "type": "object", "additionalProperties": false, "properties": { "version": { "type": "integer" }, "description": { "type": "string" }, "expanded": { "type": "string" }, "namespace": { "type": "string" Dulaunoy & Iklody Expires June 2, 2018 [Page 13] Internet-Draft MISP taxonomy format November 2017 }, "exclusive": { "type": "boolean" }, "type": { "type": "array", "uniqueItems": true, "items": { "type": "string", "enum": [ "org", "user", "attribute", "event" ] } }, "refs": { "type": "array", "uniqueItems": true, "items": { "type": "string" } }, "predicates": { "$ref": "#/defs/predicates" }, "values": { "$ref": "#/defs/values" } }, "required": [ "namespace", "description", "version", "predicates" ] } 6. Acknowledgements The authors wish to thank all the MISP community who are supporting the creation of open standards in threat intelligence sharing. Dulaunoy & Iklody Expires June 2, 2018 [Page 14] Internet-Draft MISP taxonomy format November 2017 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4627] Crockford, D., "The application/json Media Type for JavaScript Object Notation (JSON)", RFC 4627, DOI 10.17487/RFC4627, July 2006, . 7.2. Informative References [JSON-SCHEMA] "JSON Schema: A Media Type for Describing JSON Documents", 2016, . [machine-tags] "Machine tags", 2007, . [MISP-P] MISP, "MISP Project - Malware Information Sharing Platform and Threat Sharing", . [MISP-T] MISP, "MISP Taxonomies - shared and common vocabularies of tags", . Authors' Addresses Alexandre Dulaunoy Computer Incident Response Center Luxembourg 16, bd d'Avranches Luxembourg L-1611 Luxembourg Phone: +352 247 88444 Email: alexandre.dulaunoy@circl.lu Dulaunoy & Iklody Expires June 2, 2018 [Page 15] Internet-Draft MISP taxonomy format November 2017 Andras Iklody Computer Incident Response Center Luxembourg 16, bd d'Avranches Luxembourg L-1611 Luxembourg Phone: +352 247 88444 Email: andras.iklody@circl.lu Dulaunoy & Iklody Expires June 2, 2018 [Page 16]