| Individual Submission | T. Takahashi |
| Internet-Draft | NICT |
| Intended status: Standards Track | K. Landfield |
| McAfee | |
| T. Millar | |
| USCERT | |
| Y. Kadobayashi | |
| NICT | |
| Oct 29, 2011 |
IODEF-extension to support structured cybersecurity information
draft-takahashi-mile-sci-02.txt
This document extends the Incident Object Description Exchange Format (IODEF) defined in RFC 5070 [RFC5070] to facilitate enriched cybersecurity information exchange among cybersecurity entities by embedding structured information formatted by specifications, including CAPEC™ [CAPEC], CEE™ [CEE], CPE™ [CPE], CVE® [CVE], CVRF [CVRF], CVSS [CVSS], CWE™ [CWE], CWSS™ [CWSS], ISO/IEC 19770-2 [ISOIEC19770-2], OCIL [OCIL], OVAL® [OVAL], XCCDF [XCCDF], and XDAS [XDAS].
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."
Copyright (c) 2011 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.
Cyber attacks are getting more sophisticated, and their numbers are increasing day by day. To cope with such situation, incident information needs to be reported, exchanged, and shared among organizations. IODEF is one of the tools enabling such exchange, and is already in use.
To efficiently run cybersecurity operations, these exchanged information needs to be machine-readable. IODEF provides a structured means to describe the information, but it needs to embed various non-structured such information in order to convey detailed information. Further structure within IODEF increases IODEF documents' machine-readability and thus facilitates streamlining cybersecurity operations.
On the other hand, there exist various other activities facilitating detailed and structured description of cybersecurity information, major of which includes CAPEC [CAPEC], CEE [CEE], CPE [CPE], CVE [CVE], CVRF [CVRF], CVSS [CVSS], CWE [CWE], CWSS [CWSS], ISO/IEC 19770-2 [ISOIEC19770-2], OCIL [OCIL], OVAL [OVAL], XCCDF [XCCDF], and XDAS [XDAS]. Since such structured description facilitates cybersecurity operations, it would be beneficial to embed and convey these information inside IODEF document.
To enable that, this document extends the IODEF to embed and convey various structured cybersecurity information, with which cybersecurity operations can be facilitated. Since IODEF defines a flexible and extensible format and supports a granular level of specificity, this document defines an extension to IODEF instead of defining a new report format. For clarity, and to eliminate duplication, only the additional structures necessary for describing the exchange of such structured information are provided.
The terminology used in this document follows the one defined in RFC 5070 [RFC5070].
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].
To maintain cybersecurity, organization needs to exchange cybersecurity information, which includes the following information: attack pattern, platform information, vulnerability and weakness, countermeasure instruction, computer event log, and the severity.
IODEF provides a scheme to exchange such information among interested parties. However, the detailed common format to describe such information is not defined in the IODEF base document.
On the other hand, to describe those information and to facilitate exchange, a structured format for that is already available. Major of them are CAPEC, CEE, CPE, CVE, CVRF, CVSS, CWE, CWSS, OVAL, and XCCDF. By embedding them into the IODEF document, the document can convey more detailed contents to the receivers, and the document can be easily reused.
These structured cybersecurity information facilitates cybersecurity operation at the receiver side. Since the information is machine-readable, the data can be processed by computers. That expedites the automation of cybersecurity operations
For instance, an organization wishing to report a security incident wants to describe what vulnerability was exploited. Then the sender can simply use IODEF, where an CAPEC record is embedded instead of describing everything in free format text. Receiver can also identify the needed details of the attack pattern by looking up some of the xml tags defined by CAPEC. Receiver can accumulate the attack pattern information (CAPEC record) in its database and could distribute it to the interested parties if needed, without needing human interventions.
This draft extends IODEF to embed structured cybersecurity information by introducing new classes, with which these information can be embedded inside IODEF document as element contents of AdditionalData and RecordItem classes.
This extension intends to embed various structured cybersecurity information. The below table describes the initial list of supported specifications and their IDs, versions, and namespaces; future assignments are to be made through Expert Review, as requested in Section 7.
ID Specification Name Version Namespace
--------- ---------------------- ------- ------------------------
CAPEC_1.6 Common Attack Pattern 1.6 http://capec.mitre.org
Enumeration and /observables
Classification (CAPEC)
CEE_0.6 Common Event Expression 0.6 http://cee.mitre.org
(CEE)
CPE_2.3 Common Platform 2.3 http://cpe.mitre.org
Enumeration (CPE) /dictionary/2.0
CVE_1.0 Common Vulnerability 1.0 http://cve.mitre.org
and Exposures (CVE) /cve/downloads/1.0
CVRF_1.0 Common Vulnerability 1.0 http://www.icasi.org
Reporting Format /CVRF/schema/cvrf/1.0
(CVRF)
CVSS_2.0 Common Vulnerability 2 http://scap.nist.gov
Scoring System (CVSS) /schema/cvss-v2/1.0
CWE_5.0 Common Weakness 5.1 N/A
Enumeration (CWE)
CWSS_0.8 Common Weakness 0.8 N/A
Scoring System (CWSS)
OCIL_2.0 Open Checklist 2.0 http://scap.nist.gov
Interactive Language /schema/ocil/2.0
(OCIL)
OVAL_5.10 Open Vulnerability and 5.10 http://oval.mitre.org
Assessment Language /XMLSchema
(OVAL) /oval-definitions-5
XCCDF_1.2 Extensible 1.2 http://checklists.nist
Configuration .gov/xccdf/1.2
Checklist Description
Format (XCCDF)
XDAS_1998 Distributed Audit 1998 N/A
Service (XDAS)
19770-2 ISO/IEC 19770 Part 2 N/A
This extension inherits all of the data types defined in the IODEF model. One data type is added: EM_XML.
An embedded complete XML document is represented by the EM_XML data type. The elements of the document must match its root namespace element.
The IODEF Incident element [RFC5070] is summarized below. It is expressed in Unified Modeling Language (UML) syntax as used in the IODEF specification. The UML representation is for illustrative purposes only; elements are specified in XML as defined in Appendix A.
+--------------------+
| Incident |
+--------------------+
| ENUM purpose |<>---------[ IncidentID ]
| STRING ext-purpose |<>--{0..1}-[ AlternativeID ]
| ENUM lang |<>--{0..1}-[ RelatedActivity ]
| ENUM restriction |<>--{0..1}-[ DetectTime ]
| |<>--{0..1}-[ StartTime ]
| |<>--{0..1}-[ EndTime ]
| |<>---------[ ReportTime ]
| |<>--{0..*}-[ Description ]
| |<>--{1..*}-[ Assessment ]
| |<>--{0..*}-[ Method ]
| | |<>--[ AdditionalData ]
| | |<>--[ AttackPattern ]
| | |<>--[ Vulnerability ]
| | |<>--[ Weakness ]
| |<>--{1..*}-[ Contact ]
| |<>--{0..*}-[ EventData ]
| | |<>--[ Flow ]
| | | |<>--[ System ]
| | | |<>--[ AdditionalData ]
| | | |<>--[ PlatformID ]
| | |<>--[ Expectation ]
| | |<>--[ Record ]
| | |<>--[ RecordData ]
| | |<>--[ RecordItem ]
| | |<>--[ EventReport ]
| |<>--{0..1}-[ History ]
| |<>--{0..*}-[ AdditionalData ]
| | |<>--[ Remediation ]
+--------------------+
This extension defines the following seven elements.
An AttackPattern consists of an extension to the Incident.Method.AdditionalData element with a dtype of "xml". The extension describes attack patterns of incidents or events.
It is recommended that Method class SHOULD contain one or more of the extension elements whenever available.
An AttackPattern class is structured as follows.
+------------------------+ | AttackPattern | +------------------------+ | STRING Version |<>--(0..*)-[ Record ] | ENUM SpecificationID |<>--(0..*)-[ Reference ] | STRING AttackPatternID |<>--(0..*)-[ PlatformID ] +------------------------+
This class has the following attributes.
The AttackPattern class is composed of the following aggregate classes.
Writers/senders MUST ensure the specification name and version identified by the SpecificationID are consistent with the contents of the Record; if a reader/receiver detects an inconsistency, it SHOULD prefer the specification name and version derived from the content, and SHOULD log the inconsistency so a human can correct the problem.
A PlatformID identifies a software platform. It is recommended that AttackPattern, Vulnerability, Weakness, and System classes contain this elements whenever available.
A PlatformID element is structured as follows.
+----------------------+ | PlatformID | +----------------------+ | STRING Version |<>--(1..*)-[ ID ] | ENUM SpecificationID | +----------------------+
This class has the following attributes.
This class is composed of the following aggregate classes.
Writers/senders MUST ensure the specification name and version identified by the SpecificationID are consistent with the contents of the ID; if a reader/receiver detects an inconsistency, it SHOULD prefer the specification name and version derived from the content, and SHOULD log the inconsistency so a human can correct the problem.
A Vulnerability consists of an extension to the Incident.Method.AdditionalData element with a dtype of "xml". The extension describes the (candidate) vulnerabilities of incidents or events.
It is recommended that Method class SHOULD contain one or more of the extension elements whenever available.
A Vulnerability element is structured as follows.
+------------------------+ | Vulnerability | +------------------------+ | STRING Version |<>--(0..*)-[ Record ] | ENUM SpecificationID |<>--(0..*)-[ Reference ] | STRING VulnerabilityID |<>--(0..*)-[ PlatformID ] | |<>--(0..*)-[ Scoring ] +------------------------+
This class has the following attributes.
This class is composed of the following aggregate classes.
A Scoring class describes the scores of the severity in terms of security. It is recommended that Vulnerability and Weakness classes contain the elements whenever available.
A Scoring class is structured as follows.
+----------------------+ | Scoring | +----------------------+ | STRING Version |<>---------[ Score ] | ENUM SpecificationID | +----------------------+
This class has two attributes.
This class is composed of an aggregate class.
Writers/senders MUST ensure the specification name and version identified by the SpecificationID are consistent with the contents of the Score; if a reader/receiver detects an inconsistency, it SHOULD prefer the specification name and version derived from the content, and SHOULD log the inconsistency so a human can correct the problem.
A Weakness consists of an extension to the Incident.Method.AdditionalData element with a dtype of "xml". The extension describes the weakness types of incidents or events.
It is recommended that Method class SHOULD contain one or more of the extension elements whenever available.
A Weakness element is structured as follows.
+----------------------+ | Weakness | +----------------------+ | STRING Version |<>--(0..*)-[ Record ] | ENUM SpecificationID |<>--(0..*)-[ Reference ] | STRING WeaknessID |<>--(0..*)-[ PlatformID ] | |<>--(0..*)-[ Scoring ] +----------------------+
This class has the following attributes.
This class is composed of the following aggregate classes.
An EventReport consists of an extension to the Incident.EventData.Record.RecordData.RecordItem element with a dtype of "xml". The extension embeds structured event reports.
It is recommended that RecordItem class SHOULD contain one or more of the extension elements whenever available.
An EventReport element is structured as follows.
+----------------------+ | EventReport | +----------------------+ | STRING Version |<>--(0..*)-[ Record ] | ENUM SpecificationID |<>--(0..*)-[ Reference ] +----------------------+
This class has the following attributes.
This class is composed of three aggregate classes.
This class MUST contain at least one of Record or Reference elements. Writers/senders MUST ensure the specification name and version identified by the SpecificationID are consistent with the contents of the Record; if a reader/receiver detects an inconsistency, it SHOULD prefer the specification name and version derived from the content, and SHOULD log the inconsistency so a human can correct the problem.
A Remediation consists of an extension to the Incident.AdditionalData element with a dtype of "xml". The extension elements describes incident remediation information including instructions. Note that the term remediation includes a range of concepts, e.g., valudation.
It is recommended that Incident class SHOULD contain one or more of this extension elements whenever available.
A Remediation class is structured as follows.
+----------------------+ | Remediation | +----------------------+ | STRING Version |<>--(0..*)-[ Record ] | ENUM SpecificationID |<>--(0..*)-[ Reference ] +----------------------+
This class has an attribute.
This class is composed of three aggregate classes.
This class MUST contain at least either of Record and Reference elements. Writers/senders MUST ensure the specification name and version identified by the SpecificationID are consistent with the contents of the Record; if a reader/receiver detects an inconsistency, it SHOULD prefer the specification name and version derived from the content, and SHOULD log the inconsistency so a human can correct the problem.
This section provides examples of an incident encoded in the IODEF. These examples do not necessarily represent the only way to encode a particular incident.
An example of a CSIRT reporting an attack.
<?xml version="1.0" encoding="UTF-8"?>
<IODEF-Document version="1.00" lang="en"
xmlns="urn:ietf:params:xml:ns:iodef-1.0"
xmlns:iodef="urn:ietf:params:xml:ns:iodef-1.0"
xmlns:iodef-sci="urn:ietf:params:xml:ns:iodef-sci-1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Incident purpose="reporting">
<IncidentID name="csirt.example.com">189493</IncidentID>
<ReportTime>2001-09-13T23:19:24+00:00</ReportTime>
<Description>Incident report in company xx</Description>
<!-- An administrative privilege was attempted, but failed -->
<Assessment>
<Impact completion="failed" type="admin"/>
</Assessment>
<Method>
<Description>Structured information on attack pattern, exploited
vulnerability, and weakness</Description>
<AdditionalData dtype="xml">
<iodef-sci:AttackPattern SpecificationID="CAPEC_1.6"
AttackPatternID="CAPEC-14">
<iodef-sci:Record>[CAPEC-formatted data]</iodef-sci:Record>
<Reference>
<ReferenceName>Link to Capec-14</ReferenceName>
<URL>http://capec.mitre.org/data/definitions/14.html</URL>
</Reference>
</iodef-sci:AttackPattern>
<iodef-sci:Vulnerability SpecificationID="CVE_1.0"
VulnerabilityID="CVE-2010-3654">
<iodef-sci:Record>[CVE-formatted data]</iodef-sci:Record>
<iodef-sci:PlatformID SpecificationID="CPE_2.3">
<iodef-sci:ID>[CPE ID]</iodef-sci:ID>
</iodef-sci:PlatformID>
<iodef-sci:Scoring SpecificationID="CVSS_2.0">
<iodef-sci:Score>[CVSS scores]</iodef-sci:Score>
</iodef-sci:Scoring>
</iodef-sci:Vulnerability>
<iodef-sci:Weakness SpecificationID="CWE_5.0"
WeaknessID="CWE-119">
<iodef-sci:Record>[CWE-formatted data]</iodef-sci:Record>
<iodef-sci:Scoring SpecificationID="CWSS_0.8">
<iodef-sci:Score>[CWSS scores]</iodef-sci:Score>
</iodef-sci:Scoring>
</iodef-sci:Weakness>
</AdditionalData>
</Method>
<Contact role="creator" type="organization">
<ContactName>Example.com CSIRT</ContactName>
<RegistryHandle registry="arin">example-com</RegistryHandle>
<Email>contact@csirt.example.com</Email>
</Contact>
<EventData>
<Flow>
<System category="source">
<Node>
<Address category="ipv4-addr">192.0.2.200</Address>
<Counter type="event">57</Counter>
</Node>
</System>
<System category="target">
<Node>
<Address category="ipv4-net">192.0.2.16/28</Address>
</Node>
<Service ip_protocol="6">
<Port>80</Port>
</Service>
<AdditionalData dtype="xml">
<iodef-sci:PlatformID SpecificationID="CPE_2.3">
<iodef-sci:ID>[CPE ID]</iodef-sci:ID>
</iodef-sci:PlatformID>
</AdditionalData>
</System>
</Flow>
<Expectation action="block-host" />
<Expectation action="other"/>
<!-- <RecordItem> has an excerpt from a log -->
<Record>
<RecordData>
<DateTime>2001-09-13T18:11:21+02:00</DateTime>
<Description>a Web-server event record</Description>
<RecordItem dtype="xml">
<iodef-sci:EventReport SpecificationID="CEE_0.6">
<iodef-sci:Record>[CEE-formatted data]</iodef-sci:Record>
</iodef-sci:EventReport>
</RecordItem>
</RecordData>
</Record>
</EventData>
<History>
<!-- Contact was previously made with the source network owner -->
<HistoryItem action="contact-source-site">
<DateTime>2001-09-14T08:19:01+00:00</DateTime>
<Description>Notification sent to
constituency-contact@192.0.2.200</Description>
</HistoryItem>
</History>
<AdditionalData dtype="xml">
<iodef-sci:Remediation SpecificationID="OVAL_5.10">
<iodef-sci:Record>[OVAL-formatted data]</iodef-sci:Record>
</iodef-sci:Remediation>
<iodef-sci:Remediation SpecificationID="XCCDF_1.2">
<iodef-sci:Record>[XCCDF-formatted data]</iodef-sci:Record>
</iodef-sci:Remediation>
</AdditionalData>
</Incident>
</IODEF-Document>
This document specifies a format for encoding a particular class of security incidents appropriate for exchange across organizations. As merely a data representation, it does not directly introduce security issues. However, it is guaranteed that parties exchanging instances of this specification will have certain concerns. For this reason, the underlying message format and transport protocol used MUST ensure the appropriate degree of confidentiality, integrity, and authenticity for the specific environment.
Organizations that exchange data using this document are URGED to develop operating procedures that document the following areas of concern.
The underlying messaging format and protocol used to exchange instances of the IODEF MUST provide appropriate guarantees of confidentiality, integrity, and authenticity. The use of a standardized security protocol is encouraged. The Real-time Inter- network Defense (RID) protocol [RFC6045] and its associated transport binding [RFC6046] provide such security.
The critical security concerns are that these structured information may be falsified or they may become corrupt during transit. In areas where transmission security or secrecy is questionable, the application of a digital signature and/or message encryption on each report will counteract both of these concerns. We expect that each exchanging organization will determine the need, and mechanism, for transport protection.
In some instances, data values in particular elements may contain data deemed sensitive by the reporter. Although there are no general-purpose rules on when to mark certain values as "private" or "need-to-know" via the iodef:restriction attribute, the reporter is cautioned not to apply element-level sensitivity markings unless they believe the receiving party (i.e., the party they are exchanging the event report data with) has a mechanism to adequately safeguard and process the data as marked.
This document uses URNs to describe XML namespaces and XML schemata conforming to a registry mechanism described in [RFC3688].
Registration request for the IODEF structured cybersecurity information extension namespace:
Registration request for the IODEF structured cybersecurity information extension XML schema:
Request for managing a namespace list:
The following groups and individuals, listed alphabetically, contributed substantially to this document and should be recognized for their efforts.
The XML Schema describing the elements defined in the Extension Definition section is given here. Each of the examples in Section 5 should be verified to validate against this schema by automated tools. [Note: this section will be thoroughly checked later.]
<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema targetNamespace="urn:ietf:params:xml:ns:iodef-sci-1.0"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:iodef="urn:ietf:params:xml:ns:iodef-1.0"
xmlns:iodef-sci="urn:ietf:params:xml:ns:iodef-sci-1.0"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xsd:import
namespace="urn:ietf:params:xml:ns:iodef-1.0"
schemaLocation="urn:ietf:params:xml:schema:iodef-1.0"/>
<!--================================================================
== Scoring Class ==
==================================================================-->
<xsd:element name="Scoring">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Score" type="xsd:anyType"/>
</xsd:sequence>
<xsd:attribute name="Version" type="xsd:string" use="optional"
default="1.00"/>
<xsd:attribute name="SpecificationID" type="xsd:string"
use="required"/>
</xsd:complexType>
</xsd:element>
<!--================================================================
== AttackPattern Class ==
==================================================================-->
<xsd:element name="AttackPattern">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Record" type="xsd:anyType" minOccurs="0"
maxOccurs="unbounded"/>
<xsd:element name="Reference" ref="iodef:Reference"
minOccurs="0" maxOccurs="unbounded"/>
<xsd:element name="PlatformID" ref="iodef-sci:PlatformID"
minOccurs="0" maxOccurs="unbounded"/>
</xsd:sequence>
<xsd:attribute name="Version" type="xsd:string" use="optional"
default="1.00"/>
<xsd:attribute name="SpecificationID" type="xsd:string" use="required"/>
<xsd:attribute name="AttackPatternID" type="xsd:string" use="optional"/>
</xsd:complexType>
</xsd:element>
<!--================================================================
== Vulnerability Class ==
==================================================================-->
<xsd:element name="Vulnerability">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Record" type="xsd:anyType" minOccurs="0"
maxOccurs="unbounded"/>
<xsd:element name="Reference" ref="iodef:Reference"
minOccurs="0" maxOccurs="unbounded"/>
<xsd:element name="PlatformID" ref="iodef-sci:PlatformID"
minOccurs="0" maxOccurs="unbounded"/>
<xsd:element name="Scoring" ref="iodef-sci:Scoring"
minOccurs="0" maxOccurs="unbounded"/>
</xsd:sequence>
<xsd:attribute name="Version" type="xsd:string"
use="optional" default="1.00"/>
<xsd:attribute name="SpecificationID" type="xsd:string"
use="required"/>
<xsd:attribute name="VulnerabilityID" type="xsd:string"
use="optional"/>
</xsd:complexType>
</xsd:element>
<!--=================================================================
== Weakness Class ==
==================================================================-->
<xsd:element name="Weakness">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="Record" type="xsd:anyType" minOccurs="0"
maxOccurs="unbounded"/>
<xsd:element name="Reference" ref="iodef:Reference"
minOccurs="0" maxOccurs="unbounded"/>
<xsd:element name="PlatformID" ref="iodef-sci:PlatformID"
minOccurs="0" maxOccurs="unbounded"/>
<xsd:element name="Scoring" ref="iodef-sci:Scoring"
minOccurs="0" maxOccurs="unbounded"/>
</xsd:sequence>
<xsd:attribute name="Version" type="xsd:string" use="optional"
default="1.00"/>
<xsd:attribute name="SpecificationID" type="xsd:string"
use="required"/>
<xsd:attribute name="WeaknessID" type="xsd:string"
use="optional"/>
</xsd:complexType>
</xsd:element>
<!--=================================================================
== PlatformID Class ==
==================================================================-->
<xsd:element name="PlatformID">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="ID" type="xsd:string" minOccurs="1"
maxOccurs="unbounded"/>
</xsd:sequence>
<xsd:attribute name="Version" type="xsd:string" use="optional"
default="1.00"/>
<xsd:attribute name="SpecificationID" type="xsd:string"
use="required"/>
</xsd:complexType>
</xsd:element>
<!--================================================================
== EventReport Class ==
=================================================================-->
<xsd:element name="EventReport">
<xsd:complexType>
<xsd:sequence>
<xsd:choice>
<xsd:element name="Record" type="xsd:anyType"/>
<xsd:element name="Reference" ref="iodef:Reference"/>
</xsd:choice>
</xsd:sequence>
<xsd:attribute name="Version" type="xsd:string"
use="optional" default="1.00"/>
<xsd:attribute name="SpecificationID" type="xsd:string"
use="required"/>
</xsd:complexType>
</xsd:element>
<!--================================================================
== Remediation Class ==
=================================================================-->
<xsd:element name="Remediation">
<xsd:complexType>
<xsd:sequence>
<xsd:choice>
<xsd:element name="Record" type="xsd:anyType"/>
<xsd:element name="Reference" ref="iodef:Reference"/>
</xsd:choice>
</xsd:sequence>
<xsd:attribute name="Version" type="xsd:string"
use="optional" default="1.00"/>
<xsd:attribute name="SpecificationID" type="xsd:string"
use="required"/>
</xsd:complexType>
</xsd:element>
</xsd:schema>
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC5070] | Danyliw, R., Meijer, J. and Y. Demchenko, "The Incident Object Description Exchange Format", RFC 5070, December 2007. |
| [RFC6045] | Moriarty, K., "Real-time Inter-network Defense (RID)", RFC 6045, November 2010. |
| [RFC6046] | Moriarty, K. and B. Trammell, "Transport of Real-time Inter-network Defense (RID) Messages", RFC 6046, November 2010. |