event.yml

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---
- name: event
  title: Event
  group: 2
  short: Fields breaking down the event details.
  description: >
    The event fields are used for context information about the log or metric event itself.

    A log is defined as an event containing details of something that happened.
    Log events must include the time at which the thing happened.
    Examples of log events include a process starting on a host,
    a network packet being sent from a source to a destination,
    or a network connection between a client and a server being initiated or closed.
    A metric is defined as an event containing one or more numerical measurements
    and the time at which the measurement was taken. Examples of metric events include
    memory pressure measured on a host and device temperature.
    See the `event.kind` definition in this section for additional details about
    metric and state events.
  type: group

  fields:

    - name: id
      level: core
      type: keyword
      description: >
        Unique ID to describe the event.
      example: 8a4f500d

    - name: code
      level: extended
      type: keyword
      short: Identification code for this event.
      description: >
        Identification code for this event, if one exists.

        Some event sources use event codes to identify messages unambiguously,
        regardless of message language or wording adjustments over time.
        An example of this is the Windows Event ID.
      example: 4648

    - name: kind
      level: core
      type: keyword
      short: The kind of the event. The highest categorization field in the hierarchy.
      description: >
        This is one of four ECS Categorization Fields, and indicates the
        highest level in the ECS category hierarchy.

        `event.kind` gives high-level information about what type of information the
        event contains, without being specific to the contents of the event.
        For example, values of this field distinguish alert events from
        metric events.

        The value of this field can be used to inform how these kinds of events should be handled.
        They may warrant different retention, different access control, it may also
        help understand whether the data coming in at a regular interval or not.
      example: alert
      allowed_values:
        - name: alert
          description: >
            This value indicates an event such as an alert or notable event,
            triggered by a detection rule executing externally to the Elastic Stack.

            `event.kind:alert` is often populated for events coming from firewalls,
            intrusion detection systems, endpoint detection and response systems, and so on.

            This value is not used by Elastic solutions for alert documents
            that are created by rules executing within the Kibana alerting framework.
        - name: enrichment
          description: >
            The `enrichment` value indicates an event collected to provide additional
            context, often to other events.

            An example is collecting indicators of compromise (IOCs) from a threat
            intelligence provider with the intent to use those values to enrich other
            events. The IOC events from the intelligence provider should be categorized
            as `event.kind:enrichment`.
        - name: event
          description: >
            This value is the most general and most common value for this field.
            It is used to represent events that indicate that something happened.
        - name: metric
          description: >
            This value is used to indicate that this event describes a numeric measurement
            taken at given point in time.

            Examples include CPU utilization, memory usage, or device temperature.

            Metric events are often collected on a predictable frequency, such as once
            every few seconds, or once a minute, but can also be used to
            describe ad-hoc numeric metric queries.
        - name: state
          description: >
            The state value is similar to metric, indicating that this event describes a
            measurement taken at given point in time, except that the measurement does not
            result in a numeric value, but rather one of a fixed set of categorical values
            that represent conditions or states.

            Examples include periodic events reporting Elasticsearch cluster state (green/yellow/red),
            the state of a TCP connection (open, closed, fin_wait, etc.), the state of a host with respect
            to a software vulnerability (vulnerable, not vulnerable), and the state of a system
            regarding compliance with a regulatory standard (compliant, not compliant).

            Note that an event that describes a change of state would not use `event.kind:state`,
            but instead would use 'event.kind:event' since a state change fits the more general
            event definition of something that happened.

            State events are often collected on a predictable frequency, such as once
            every few seconds, once a minute, once an hour, or once a day, but can also be used to
            describe ad-hoc state queries.
        - name: pipeline_error
          description: >
            This value indicates that an error occurred during the ingestion of this event,
            and that event data may be missing, inconsistent, or incorrect.
            `event.kind:pipeline_error` is often associated with parsing errors.
        - name: signal
          description: >
            This value is used by Elastic solutions (e.g., Security, Observability) for alert documents
            that are created by rules executing within the Kibana alerting framework.

            Usage of this value is reserved, and data ingestion pipelines must not populate
            `event.kind` with the value "signal".

    - name: category
      level: core
      type: keyword
      short: Event category. The second categorization field in the hierarchy.
      description: >
        This is one of four ECS Categorization Fields, and indicates the
        second level in the ECS category hierarchy.

        `event.category` represents the "big buckets" of ECS categories. For example,
        filtering on `event.category:process` yields all events relating to process activity.
        This field is closely related to `event.type`, which is used as a subcategory.

        This field is an array. This will allow proper categorization of some events
        that fall in multiple categories.
      example: authentication
      normalize:
        - array
      allowed_values:
        - name: authentication
          description: >
            Events in this category are related to the challenge and response process
            in which credentials are supplied and verified to allow the creation of a session.
            Common sources for these logs are Windows event logs and ssh logs.
            Visualize and analyze events in this category to look for failed logins,
            and other authentication-related activity.
          expected_event_types:
            - start
            - end
            - info
        - name: configuration
          description: >
            Events in the configuration category have to deal with creating, modifying, or
            deleting the settings or parameters of an application, process, or system.

            Example sources include security policy change logs, configuration auditing logging,
            and system integrity monitoring.
          expected_event_types:
            - access
            - change
            - creation
            - deletion
            - info
        - name: database
          description: >
            The database category denotes events and metrics relating to a data storage
            and retrieval system. Note that use of this category is not limited to
            relational database systems. Examples include event logs from MS SQL, MySQL,
            Elasticsearch, MongoDB, etc. Use this category to visualize and analyze
            database activity such as accesses and changes.
          expected_event_types:
            - access
            - change
            - info
            - error
        - name: driver
          description: >
            Events in the driver category have to do with operating system device drivers
            and similar software entities such as Windows drivers, kernel extensions, kernel modules, etc.

            Use events and metrics in this category to visualize and analyze driver-related
            activity and status on hosts.
          expected_event_types:
            - change
            - end
            - info
            - start
        - name: email
          description: >
            This category is used for events relating to email messages, email attachments,
            and email network or protocol activity.

            Emails events can be produced by email security gateways, mail transfer agents, email
            cloud service providers, or mail server monitoring applications.
          expected_event_types:
            - info
        - name: file
          description: >
            Relating to a set of information that has been created on, or has existed on a filesystem.
            Use this category of events to visualize and analyze the creation, access,
            and deletions of files. Events in this category can come
            from both host-based and network-based sources. An example source of a network-based
            detection of a file transfer would be the Zeek file.log.
          expected_event_types:
            - change
            - creation
            - deletion
            - info
        - name: host
          description: >
            Use this category to visualize and analyze information such as host inventory
            or host lifecycle events.

            Most of the events in this category can usually be observed from the outside,
            such as from a hypervisor or a control plane's point of view. Some can also
            be seen from within, such as "start" or "end".

            Note that this category is for information about hosts themselves;
            it is not meant to capture activity "happening on a host".
          expected_event_types:
            - access
            - change
            - end
            - info
            - start
        - name: iam
          description: >
            Identity and access management (IAM) events relating to users, groups, and administration.
            Use this category to visualize and analyze IAM-related logs and data from active directory,
            LDAP, Okta, Duo, and other IAM systems.
          expected_event_types:
            - admin
            - change
            - creation
            - deletion
            - group
            - info
            - user
        - name: intrusion_detection
          description: >
            Relating to intrusion detections from IDS/IPS systems and functions,
            both network and host-based. Use this category to visualize and analyze
            intrusion detection alerts from systems such as Snort, Suricata,
            and Palo Alto threat detections.
          expected_event_types:
            - allowed
            - denied
            - info
        - name: malware
          description: >
            Malware detection events and alerts. Use this category to visualize and analyze
            malware detections from EDR/EPP systems such as Elastic Endpoint Security,
            Symantec Endpoint Protection, Crowdstrike, and network IDS/IPS systems
            such as Suricata, or other sources of malware-related events such as
            Palo Alto Networks threat logs and Wildfire logs.
          expected_event_types:
            - info
        - name: network
          description: >
            Relating to all network activity, including network connection lifecycle,
            network traffic, and essentially any event that includes an IP address. Many events
            containing decoded network protocol transactions fit into this category.
            Use events in this category to visualize or analyze counts of network ports,
            protocols, addresses, geolocation information, etc.
          expected_event_types:
            - access
            - allowed
            - connection
            - denied
            - end
            - info
            - protocol
            - start
        - name: package
          description: >
            Relating to software packages installed on hosts. Use this category to
            visualize and analyze inventory of software installed on various hosts,
            or to determine host vulnerability in the absence of vulnerability scan data.
          expected_event_types:
            - access
            - change
            - deletion
            - info
            - installation
            - start
        - name: process
          description: >
            Use this category of events to visualize and analyze process-specific
            information such as lifecycle events or process ancestry.
          expected_event_types:
            - access
            - change
            - end
            - info
            - start
        - name: registry
          description: >
            Having to do with settings and assets stored in the Windows registry.
            Use this category to visualize and analyze activity such as registry access and modifications.
          expected_event_types:
            - access
            - change
            - creation
            - deletion
        - name: session
          description: >
            The session category is applied to events and metrics regarding logical persistent connections to hosts and services.
            Use this category to visualize and analyze interactive or automated persistent connections between assets.
            Data for this category may come from Windows Event logs, SSH logs, or stateless sessions such as HTTP cookie-based sessions, etc.
          expected_event_types:
            - start
            - end
            - info
        - name: threat
          description: >
            Use this category to visualize and analyze events describing threat actors' targets, motives, or behaviors.
          expected_event_types:
            - indicator
        - name: web
          description: >
            Relating to web server access. Use this category to create a dashboard of
            web server/proxy activity from apache, IIS, nginx web servers, etc.
            Note: events from network observers such as Zeek http log may also be included
            in this category.
          expected_event_types:
            - access
            - error
            - info

    - name: action
      level: core
      type: keyword
      short: The action captured by the event.
      description: >
        The action captured by the event.

        This describes the information in the event. It is more specific than
        `event.category`. Examples are `group-add`, `process-started`,
        `file-created`. The value is normally defined by the implementer.
      example: user-password-change

    - name: outcome
      level: core
      type: keyword
      short: The outcome of the event. The lowest level categorization field in the hierarchy.
      description: >
        This is one of four ECS Categorization Fields, and indicates the
        lowest level in the ECS category hierarchy.

        `event.outcome` simply denotes whether the event represents a success or a failure from
        the perspective of the entity that produced the event.

        Note that when a single transaction is described in multiple events, each event may
        populate different values of `event.outcome`, according to their perspective.

        Also note that in the case of a compound event (a single event that contains multiple logical events),
        this field should be populated with the value that best captures the overall success or failure from
        the perspective of the event producer.

        Further note that not all events will have an associated outcome. For example, this field is
        generally not populated for metric events, events with `event.type:info`, or any events for
        which an outcome does not make logical sense.
      example: success
      allowed_values:
        - name: failure
          description: >
            Indicates that this event describes a failed result. A common example is
            `event.category:file AND event.type:access AND event.outcome:failure`
            to indicate that a file access was attempted, but was not successful.
        - name: success
          description: >
            Indicates that this event describes a successful result. A common example is
            `event.category:file AND event.type:create AND event.outcome:success`
            to indicate that a file was successfully created.
        - name: unknown
          description: >
            Indicates that this event describes only an attempt for which the result
            is unknown from the perspective of the event producer.
            For example, if the event contains information only about the request side
            of a transaction that results in a response, populating `event.outcome:unknown`
            in the request event is appropriate.
            The unknown value should not be used when an outcome doesn't make logical sense for
            the event. In such cases `event.outcome` should not be populated.

    - name: type
      level: core
      type: keyword
      short: Event type. The third categorization field in the hierarchy.
      description: >
        This is one of four ECS Categorization Fields, and indicates the
        third level in the ECS category hierarchy.

        `event.type` represents a categorization "sub-bucket" that, when used along with
        the `event.category` field values, enables filtering events down to a level
        appropriate for single visualization.

        This field is an array. This will allow proper categorization of some events
        that fall in multiple event types.
      normalize:
        - array
      allowed_values:
        - name: access
          description: >
            The access event type is used for the subset of events within a category
            that indicate that something was accessed.
            Common examples include `event.category:database AND event.type:access`,
            or `event.category:file AND event.type:access`.
            Note for file access, both directory listings and file opens should be included
            in this subcategory. You can further distinguish access operations using the ECS
            `event.action` field.
        - name: admin
          description: >
            The admin event type is used for the subset of events within a category
            that are related to admin objects. For example, administrative changes within
            an IAM framework that do not specifically affect a user or group (e.g., adding new
            applications to a federation solution or connecting discrete forests in Active Directory)
            would fall into this subcategory.
            Common example: `event.category:iam AND event.type:change AND event.type:admin`.
            You can further distinguish admin operations using the ECS
            `event.action` field.
        - name: allowed
          description: >
            The allowed event type is used for the subset of events within a category that
            indicate that something was allowed. Common examples include
            `event.category:network AND event.type:connection AND event.type:allowed` (to indicate a network
            firewall event for which the firewall disposition was to allow the connection to complete)
            and `event.category:intrusion_detection AND event.type:allowed` (to indicate a network
            intrusion prevention system event for which the IPS disposition was to allow the connection
            to complete). You can further distinguish allowed operations using the ECS
            `event.action` field, populating with values of your choosing, such as "allow", "detect", or
            "pass".
        - name: change
          description: >
            The change event type is used for the subset of events within a category
            that indicate that something has changed. If semantics best describe an
            event as modified, then include them in this subcategory.
            Common examples include `event.category:process AND event.type:change`,
            and `event.category:file AND event.type:change`.
            You can further distinguish change operations using the ECS `event.action` field.
        - name: connection
          description: >
            Used primarily with `event.category:network` this value is used for the subset of
            network traffic that includes sufficient information for the event to be included
            in flow or connection analysis. Events in this subcategory will contain at least
            source and destination IP addresses, source and destination TCP/UDP ports, and will usually
            contain counts of bytes and/or packets transferred. Events in this subcategory may contain
            unidirectional or bidirectional information, including summary information.
            Use this subcategory to visualize and analyze network connections. Flow analysis, including
            Netflow, IPFIX, and other flow-related events fit in this subcategory. Note that firewall
            events from many Next-Generation Firewall (NGFW) devices will also fit into this subcategory.  A common filter for
            flow/connection information would be
            `event.category:network AND event.type:connection AND event.type:end` (to view or analyze all
            completed network connections, ignoring mid-flow reports). You can further distinguish connection
            events using the ECS `event.action` field, populating with values of your choosing, such as
            "timeout", or "reset".
        - name: creation
          description: >
            The "creation" event type is used for the subset of events within a category
            that indicate that something was created.
            A common example is `event.category:file AND event.type:creation`.
        - name: deletion
          description: >
            The deletion event type is used for the subset of events within a category
            that indicate that something was deleted.
            A common example is `event.category:file AND event.type:deletion`
            to indicate that a file has been deleted.
        - name: denied
          description: >
            The denied event type is used for the subset of events within a category that
            indicate that something was denied. Common examples include
            `event.category:network AND event.type:denied` (to indicate a network
            firewall event for which the firewall disposition was to deny the connection)
            and `event.category:intrusion_detection AND event.type:denied` (to indicate a network
            intrusion prevention system event for which the IPS disposition was to deny the connection
            to complete). You can further distinguish denied operations using the ECS
            `event.action` field, populating with values of your choosing, such as "blocked", "dropped", or
            "quarantined".
        - name: end
          description: >
            The end event type is used for the subset of events within a category
            that indicate something has ended.
            A common example is `event.category:process AND event.type:end`.
        - name: error
          description: >
            The error event type is used for the subset of events within a category
            that indicate or describe an error.
            A common example is `event.category:database AND event.type:error`.
            Note that pipeline errors that occur during the event ingestion process
            should not use this `event.type` value. Instead, they should use
            `event.kind:pipeline_error`.
        - name: group
          description: >
            The group event type is used for the subset of events within a category
            that are related to group objects.
            Common example: `event.category:iam AND event.type:creation AND event.type:group`.
            You can further distinguish group operations using the ECS
            `event.action` field.
        - name: indicator
          description: >
            The indicator event type is used for the subset of events within a category
            that contain details about indicators of compromise (IOCs).

            A common example is `event.category:threat AND event.type:indicator`.
        - name: info
          description: >
            The info event type is used for the subset of events within a category
            that indicate that they are purely informational, and don't report a state
            change, or any type of action. For example, an initial run of a file integrity
            monitoring system (FIM), where an agent reports all files under management,
            would fall into the "info" subcategory. Similarly, an event containing a
            dump of all currently running processes (as opposed to reporting that a process
            started/ended) would fall into the "info" subcategory.
            An additional common examples is `event.category:intrusion_detection AND event.type:info`.
        - name: installation
          description: >
            The installation event type is used for the subset of events within a category
            that indicate that something was installed.
            A common example is `event.category:package` AND `event.type:installation`.
        - name: protocol
          description: >
            The protocol event type is used for the subset of events within a category that
            indicate that they contain protocol details or analysis, beyond simply identifying the protocol.
            Generally, network events that contain specific protocol details will fall into this subcategory.
            A common example is `event.category:network AND event.type:protocol AND event.type:connection AND event.type:end`
            (to indicate that the event is a network connection event sent at the end of a connection
            that also includes a protocol detail breakdown).
            Note that events that only indicate the name or id of the protocol should not use the protocol value.
            Further note that when the protocol subcategory is used, the identified protocol is populated in
            the ECS `network.protocol` field.
        - name: start
          description: >
            The start event type is used for the subset of events within a category
            that indicate something has started. A common example is
            `event.category:process AND event.type:start`.
        - name: user
          description: >
            The user event type is used for the subset of events within a category
            that are related to user objects.
            Common example: `event.category:iam AND event.type:deletion AND event.type:user`.
            You can further distinguish user operations using the ECS
            `event.action` field.

    - name: module
      level: core
      type: keyword
      short: Name of the module this data is coming from.
      description: >
        Name of the module this data is coming from.

        If your monitoring agent supports the concept of modules or plugins to
        process events of a given source (e.g. Apache logs),
        `event.module` should contain the name of this module.
      example: apache

    - name: dataset
      level: core
      type: keyword
      short: Name of the dataset.
      description: >
        Name of the dataset.

        If an event source publishes more than one type of log or events
        (e.g. access log, error log), the dataset is used to specify which
        one the event comes from.

        It's recommended but not required to start the dataset name with
        the module name, followed by a dot, then the dataset name.
      example: apache.access

    - name: provider
      level: extended
      type: keyword
      short: Source of the event.
      description: >
        Source of the event.

        Event transports such as Syslog or the Windows Event Log typically
        mention the source of an event. It can be the name of the
        software that generated the event (e.g. Sysmon, httpd),
        or of a subsystem of the operating system (kernel, Microsoft-Windows-Security-Auditing).

      example: kernel

    - name: severity
      type: long
      level: core
      format: string
      example: 7
      short: Numeric severity of the event.
      description: >
        The numeric severity of the event according to your event source.

        What the different severity values mean can be different between sources
        and use cases.
        It's up to the implementer to make sure severities are consistent across
        events from the same source.

        The Syslog severity belongs in `log.syslog.severity.code`.
        `event.severity` is meant to represent the severity according to
        the event source (e.g. firewall, IDS).
        If the event source does not publish its own severity,
        you may optionally copy the `log.syslog.severity.code` to `event.severity`.

    - name: original
      level: core
      type: keyword
      # Unfortunately this example is not shown correctly yet as | do not work
      # in tables well
      # Is | is the representation of | it works except for cases where
      # used ticks.
      example: "Sep 19 08:26:10 host CEF:0|Security|
          threatmanager|1.0|100|
          worm successfully stopped|10|src=10.0.0.1
          dst=2.1.2.2spt=1232"
      short: Raw text message of entire event.
      description: >
          Raw text message of entire event. Used to demonstrate log integrity
          or where the full log message (before splitting it up in multiple
          parts) may be required, e.g. for reindex.

          This field is not indexed and doc_values are disabled. It cannot be
          searched, but it can be retrieved from `_source`. If users wish to
          override this and index this field, please see `Field data types`
          in the `Elasticsearch Reference`.
      index: false
      doc_values: false

    - name: hash
      level: extended
      type: keyword
      example: "123456789012345678901234567890ABCD"
      description: >
          Hash (perhaps logstash fingerprint) of raw field to be able to
          demonstrate log integrity.

    - name: duration
      level: core
      type: long
      format: duration
      input_format: nanoseconds
      output_format: asMilliseconds
      output_precision: 1
      short: Duration of the event in nanoseconds.
      description: >
        Duration of the event in nanoseconds.

        If event.start and event.end are known this value should be the
        difference between the end and start time.

    - name: sequence
      format: string
      level: extended
      type: long
      short: Sequence number of the event.
      description: >
        Sequence number of the event.

        The sequence number is a value published by some event sources, to make the
        exact ordering of events unambiguous, regardless of the timestamp precision.

    - name: timezone
      level: extended
      type: keyword
      short: Event time zone.
      description: >
        This field should be populated when the event's timestamp does not include
        timezone information already (e.g. default Syslog timestamps). It's
        optional otherwise.

        Acceptable timezone formats are: a canonical ID (e.g. "Europe/Amsterdam"),
        abbreviated (e.g. "EST") or an HH:mm differential (e.g. "-05:00").

    - name: created
      level: core
      type: date
      short: Time when the event was first read by an agent or by your pipeline.
      example: '2016-05-23T08:05:34.857Z'
      description: >
        event.created contains the date/time when the event was first read by an
        agent, or by your pipeline.

        This field is distinct from @timestamp in that @timestamp typically contain
        the time extracted from the original event.

        In most situations, these two timestamps will be slightly different.
        The difference can be used to calculate the delay between your source
        generating an event, and the time when your agent first processed it.
        This can be used to monitor your agent's or pipeline's ability to
        keep up with your event source.

        In case the two timestamps are identical, @timestamp should be used.

    - name: start
      level: extended
      type: date
      description: >
        event.start contains the date when the event started or when the
        activity was first observed.

    - name: end
      level: extended
      type: date
      description: >
        event.end contains the date when the event ended or when the activity
        was last observed.

    - name: risk_score
      level: core
      type: float
      description: >
        Risk score or priority of the event (e.g. security solutions).
        Use your system's original value here.

    - name: risk_score_norm
      level: extended
      type: float
      short: Normalized risk score or priority of the event (0-100).
      description: >
        Normalized risk score or priority of the event, on a scale of 0 to 100.

        This is mainly useful if you use more than one system that assigns
        risk scores, and you want to see a normalized value across all systems.

    - name: ingested
      level: core
      type: date
      short: Timestamp when an event arrived in the central data store.
      example: '2016-05-23T08:05:35.101Z'
      description: >
        Timestamp when an event arrived in the central data store.

        This is different from `@timestamp`, which is when the event originally
        occurred.  It's also different from `event.created`, which is meant
        to capture the first time an agent saw the event.

        In normal conditions, assuming no tampering, the timestamps should
        chronologically look like this: `@timestamp` < `event.created` < `event.ingested`.

    - name: reference
      level: extended
      type: keyword
      short: Event reference URL
      description: >
        Reference URL linking to additional information about this event.

        This URL links to a static definition of this event.
        Alert events, indicated by `event.kind:alert`, are a common use case for this field.

      example: "https://system.example.com/event/#0001234"

    - name: url
      level: extended
      type: keyword
      short: Event investigation URL
      description: >
        URL linking to an external system to continue investigation of this event.

        This URL links to another
        system where in-depth investigation of the specific occurrence of this event can take place.
        Alert events, indicated by `event.kind:alert`, are a common use case for this field.

      example: "https://mysystem.example.com/alert/5271dedb-f5b0-4218-87f0-4ac4870a38fe"

    - name: reason
      level: extended
      type: keyword
      short: Reason why this event happened, according to the source
      description: >
        Reason why this event happened, according to the source.

        This describes the why of a particular action or outcome captured in the event. Where
        `event.action` captures the action from the event, `event.reason` describes why that action
        was taken. For example, a web proxy with an `event.action` which denied the request may also
        populate `event.reason` with the reason why (e.g. `blocked site`).
      example: "Terminated an unexpected process"

    - name: agent_id_status
      level: extended
      type: keyword
      short: Validation status of the event's agent.id field.
      description: >
        Agents are normally responsible for populating the `agent.id` field value.
        If the system receiving events is capable of validating the value based
        on authentication information for the client then this field can be used
        to reflect the outcome of that validation.

        For example if the agent's connection is authenticated with mTLS and
        the client cert contains the ID of the agent to which the cert was issued
        then the `agent.id` value in events can be checked against the certificate.
        If the values match then `event.agent_id_status: verified` is added to
        the event, otherwise one of the other allowed values should be used.

        If no validation is performed then the field should be omitted.

        The allowed values are:

        `verified` - The `agent.id` field value matches expected value obtained
        from auth metadata.

        `mismatch` - The `agent.id` field value does not match the expected
        value obtained from auth metadata.

        `missing` - There was no `agent.id` field in the event to validate.

        `auth_metadata_missing` - There was no auth metadata or it was missing
        information about the agent ID.
      example: verified