The Advanced Security Information Model (ASIM) DNS normalization schema reference (Public preview)

The DNS information model is used to describe events reported by a DNS server or a DNS security system, and is used by Microsoft Sentinel to enable source-agnostic analytics.

For more information, see Normalization and the Advanced Security Information Model (ASIM).

Important

The DNS normalization schema is currently in PREVIEW. This feature is provided without a service level agreement, and is not recommended for production workloads.

The Azure Preview Supplemental Terms include additional legal terms that apply to Azure features that are in beta, preview, or otherwise not yet released into general availability.

Schema overview

The ASIM DNS schema represents DNS protocol activity. Both DNS servers and devices sending DNS requests to a DNS server log DNS activity. The DNS protocol activity includes DNS queries, DNS server updates, and DNS bulk data transfers. Since the schema represents protocol activity, it's governed by RFCs and officially assigned parameter lists, which are referenced in this article when appropriate. The DNS schema doesn't represent DNS server audit events.

The most important activity reported by DNS servers is a DNS query, for which the EventType field is set to Query.

The most important fields in a DNS event are:

• DnsQuery, which reports the domain name for which the query was issued.

• The SrcIpAddr (aliased to IpAddr), which represents the IP address from which the request was generated. DNS servers typically provide the SrcIpAddr field, but DNS clients sometimes don't provide this field and only provide the SrcHostname field.

• EventResultDetails, which reports whether the request was successful and if not, why.

• When available, DnsResponseName, which holds the answer provided by the server to the query. ASIM doesn't require parsing the response, and its format varies between sources.

  To use this field in source-agnostic content, search the content with the has or contains operators.

DNS events collected on client device may also include User and Process information.

Guidelines for collecting DNS events

DNS is a unique protocol in that it may cross a large number of computers. Also, since DNS uses UDP, requests and responses are de-coupled and aren't directly related to each other.

The following image shows a simplified DNS request flow, including four segments. A real-world request can be more complex, with more segments involved.

Since request and response segments aren't directly connected to each other in the DNS request flow, full logging can result in significant duplication.

The most valuable segment to log is the response to the client. The response provides the domain name queries, the lookup result, and the IP address of the client. While many DNS systems log only this segment, there is value in logging the other parts. For example, a DNS cache poisoning attack often takes advantage of fake responses from an upstream server.

If your data source supports full DNS logging and you've chosen to log multiple segments, adjust your queries to prevent data duplication in Microsoft Sentinel.

For example, you might modify your query with the following normalization:

_Im_Dns | where SrcIpAddr != "127.0.0.1" and EventSubType == "response"

Parsers

For more information about ASIM parsers, see the ASIM parsers overview.

Out-of-the-box parsers

To use parsers that unify all ASIM out-of-the-box parsers, and ensure that your analysis runs across all the configured sources, use the unifying parser _Im_Dns as the table name in your query.

For the list of the DNS parsers Microsoft Sentinel provides out-of-the-box refer to the ASIM parsers list.

Add your own normalized parsers

When implementing custom parsers for the Dns information model, name your KQL functions using the format vimDns<vendor><Product>. Refer to the article Managing ASIM parsers to learn how to add your custom parsers to the DNS unifying parser.

Filtering parser parameters

The DNS parsers support filtering parameters. While these parameters are optional, they can improve your query performance.

The following filtering parameters are available:

Name	Type	Description
starttime	datetime	Filter only DNS queries that ran at or after this time.
endtime	datetime	Filter only DNS queries that finished running at or before this time.
srcipaddr	string	Filter only DNS queries from this source IP address.
domain_has_any	dynamic/string	Filter only DNS queries where the domain (or query) has any of the listed domain names, including as part of the event domain. The length of the list is limited to 10,000 items.
responsecodename	string	Filter only DNS queries for which the response code name matches the provided value. For example: NXDOMAIN
response_has_ipv4	string	Filter only DNS queries in which the response field includes the provided IP address or IP address prefix. Use this parameter when you want to filter on a single IP address or prefix. Results aren't returned for sources that don't provide a response.
response_has_any_prefix	dynamic	Filter only DNS queries in which the response field includes any of the listed IP addresses or IP address prefixes. Prefixes should end with a ., for example: 10.0.. Use this parameter when you want to filter on a list of IP addresses or prefixes. Results aren't returned for sources that don't provide a response. The length of the list is limited to 10,000 items.
eventtype	string	Filter only DNS queries of the specified type. If no value is specified, only lookup queries are returned.

For example, to filter only DNS queries from the last day that failed to resolve the domain name, use:

_Im_Dns (responsecodename = 'NXDOMAIN', starttime = ago(1d), endtime=now())

To filter only DNS queries for a specified list of domain names, use:

let torProxies=dynamic(["tor2web.org", "tor2web.com", "torlink.co"]);
_Im_Dns (domain_has_any = torProxies)

Some parameter can accept both list of values of type dynamic or a single string value. To pass a literal list to parameters that expect a dynamic value, explicitly use a dynamic literal. For example: dynamic(['192.168.','10.'])

Normalized content

For a full list of analytics rules that use normalized DNS events, see DNS query security content.

Schema details

The DNS information model is aligned with the OSSEM DNS entity schema.

For more information, see the Internet Assigned Numbers Authority (IANA) DNS parameter reference.

Common ASIM fields

Important

Fields common to all schemas are described in detail in the ASIM Common Fields article.

Common fields with specific guidelines

The following list mentions fields that have specific guidelines for DNS events:

Field	Class	Type	Description
EventType	Mandatory	Enumerated	Indicates the operation reported by the record. For DNS records, this value would be the DNS op code. Example: Query
EventSubType	Optional	Enumerated	Either request or response. For most sources, only the responses are logged, and therefore the value is often response.
EventResultDetails	Mandatory	Enumerated	For DNS events, this field provides the DNS response code. Notes: - IANA doesn't define the case for the values, so analytics must normalize the case. - If the source provides only a numerical response code and not a response code name, the parser must include a lookup table to enrich with this value. - If this record represents a request and not a response, set to NA. Example: NXDOMAIN
EventSchemaVersion	Mandatory	String	The version of the schema documented here is 0.1.7.
EventSchema	Mandatory	String	The name of the schema documented here is Dns.
Dvc fields	-	-	For DNS events, device fields refer to the system that reports the DNS event.

All common fields

Fields that appear in the table below are common to all ASIM schemas. Any guideline specified above overrides the general guidelines for the field. For example, a field might be optional in general, but mandatory for a specific schema. For further details on each field, see the ASIM Common Fields article.

Class	Fields
Mandatory	- EventCount - EventStartTime - EventEndTime - EventType - EventResult - EventProduct - EventVendor - EventSchema - EventSchemaVersion - Dvc
Recommended	- EventResultDetails - EventSeverity - EventUid - DvcIpAddr - DvcHostname - DvcDomain - DvcDomainType - DvcFQDN - DvcId - DvcIdType - DvcAction
Optional	- EventMessage - EventSubType - EventOriginalUid - EventOriginalType - EventOriginalSubType - EventOriginalResultDetails - EventOriginalSeverity - EventProductVersion - EventReportUrl - EventOwner - DvcZone - DvcMacAddr - DvcOs - DvcOsVersion - DvcOriginalAction - DvcInterface - AdditionalFields - DvcDescription - DvcScopeId - DvcScope

Source system fields

Field	Class	Type	Description
Src	Alias	String	A unique identifier of the source device. This field can alias the SrcDvcId, SrcHostname, or SrcIpAddr fields. Example: 192.168.12.1
SrcIpAddr	Recommended	IP Address	The IP address of the client that sent the DNS request. For a recursive DNS request, this value would typically be the reporting device, and in most cases set to 127.0.0.1. Example: 192.168.12.1
SrcPortNumber	Optional	Integer	Source port of the DNS query. Example: 54312
IpAddr	Alias		Alias to SrcIpAddr
SrcGeoCountry	Optional	Country	The country/region associated with the source IP address. Example: USA
SrcGeoRegion	Optional	Region	The region associated with the source IP address. Example: Vermont
SrcGeoCity	Optional	City	The city associated with the source IP address. Example: Burlington
SrcGeoLatitude	Optional	Latitude	The latitude of the geographical coordinate associated with the source IP address. Example: 44.475833
SrcGeoLongitude	Optional	Longitude	The longitude of the geographical coordinate associated with the source IP address. Example: 73.211944
SrcRiskLevel	Optional	Integer	The risk level associated with the source. The value should be adjusted to a range of 0 to 100, with 0 for benign and 100 for a high risk. Example: 90
SrcOriginalRiskLevel	Optional	Integer	The risk level associated with the source, as reported by the reporting device. Example: Suspicious
SrcHostname	Recommended	String	The source device hostname, excluding domain information. Example: DESKTOP-1282V4D
Hostname	Alias		Alias to SrcHostname
SrcDomain	Recommended	String	The domain of the source device. Example: Contoso
SrcDomainType	Conditional	Enumerated	The type of SrcDomain, if known. Possible values include: - Windows (such as: contoso) - FQDN (such as: microsoft.com) Required if SrcDomain is used.
SrcFQDN	Optional	String	The source device hostname, including domain information when available. Note: This field supports both traditional FQDN format and Windows domain\hostname format. The SrcDomainType field reflects the format used. Example: Contoso\DESKTOP-1282V4D
SrcDvcId	Optional	String	The ID of the source device as reported in the record. For example: ac7e9755-8eae-4ffc-8a02-50ed7a2216c3
SrcDvcScopeId	Optional	String	The cloud platform scope ID the device belongs to. SrcDvcScopeId map to a subscription ID on Azure and to an account ID on AWS.
SrcDvcScope	Optional	String	The cloud platform scope the device belongs to. SrcDvcScope map to a subscription ID on Azure and to an account ID on AWS.
SrcDvcIdType	Conditional	Enumerated	The type of SrcDvcId, if known. Possible values include: - AzureResourceId - MDEid If multiple IDs are available, use the first one from the list, and store the others in the SrcDvcAzureResourceId and SrcDvcMDEid, respectively. Note: This field is required if SrcDvcId is used.
SrcDeviceType	Optional	Enumerated	The type of the source device. Possible values include: - Computer - Mobile Device - IOT Device - Other
SrcDescription	Optional	String	A descriptive text associated with the device. For example: Primary Domain Controller.

Source user fields

Field	Class	Type	Description
SrcUserId	Optional	String	A machine-readable, alphanumeric, unique representation of the source user. For more information, and for alternative fields for additional IDs, see The User entity. Example: S-1-12-1-4141952679-1282074057-627758481-2916039507
SrcUserScope	Optional	String	The scope, such as Microsoft Entra tenant, in which SrcUserId and SrcUsername are defined. or more information and list of allowed values, see UserScope in the Schema Overview article.
SrcUserScopeId	Optional	String	The scope ID, such as Microsoft Entra Directory ID, in which SrcUserId and SrcUsername are defined. for more information and list of allowed values, see UserScopeId in the Schema Overview article.
SrcUserIdType	Conditional	UserIdType	The type of the ID stored in the SrcUserId field. For more information and list of allowed values, see UserIdType in the Schema Overview article.
SrcUsername	Optional	Username	The source username, including domain information when available. For more information, see The User entity. Example: AlbertE
SrcUsernameType	Conditional	UsernameType	Specifies the type of the user name stored in the SrcUsername field. For more information, and list of allowed values, see UsernameType in the Schema Overview article. Example: Windows
User	Alias		Alias to SrcUsername
SrcUserType	Optional	UserType	The type of the source user. For more information, and list of allowed values, see UserType in the Schema Overview article. For example: Guest
SrcUserSessionId	Optional	String	The unique ID of the sign-in session of the Actor. Example: 102pTUgC3p8RIqHvzxLCHnFlg
SrcOriginalUserType	Optional	String	The original source user type, if provided by the source.

Source process fields

Field	Class	Type	Description
SrcProcessName	Optional	String	The file name of the process that initiated the DNS request. This name is typically considered to be the process name. Example: C:\Windows\explorer.exe
Process	Alias		Alias to the SrcProcessName Example: C:\Windows\System32\rundll32.exe
SrcProcessId	Optional	String	The process ID (PID) of the process that initiated the DNS request. Example: 48610176 Note: The type is defined as string to support varying systems, but on Windows and Linux this value must be numeric. If you are using a Windows or Linux machine and used a different type, make sure to convert the values. For example, if you used a hexadecimal value, convert it to a decimal value.
SrcProcessGuid	Optional	String	A generated unique identifier (GUID) of the process that initiated the DNS request. Example: EF3BD0BD-2B74-60C5-AF5C-010000001E00

Destination system fields

Field	Class	Type	Description
Dst	Alias	String	A unique identifier of the server that received the DNS request. This field may alias the DstDvcId, DstHostname, or DstIpAddr fields. Example: 192.168.12.1
DstIpAddr	Optional	IP Address	The IP address of the server that received the DNS request. For a regular DNS request, this value would typically be the reporting device, and in most cases set to 127.0.0.1. Example: 127.0.0.1
DstGeoCountry	Optional	Country	The country/region associated with the destination IP address. For more information, see Logical types. Example: USA
DstGeoRegion	Optional	Region	The region, or state, associated with the destination IP address. For more information, see Logical types. Example: Vermont
DstGeoCity	Optional	City	The city associated with the destination IP address. For more information, see Logical types. Example: Burlington
DstGeoLatitude	Optional	Latitude	The latitude of the geographical coordinate associated with the destination IP address. For more information, see Logical types. Example: 44.475833
DstGeoLongitude	Optional	Longitude	The longitude of the geographical coordinate associated with the destination IP address. For more information, see Logical types. Example: 73.211944
DstRiskLevel	Optional	Integer	The risk level associated with the destination. The value should be adjusted to a range of 0 to 100, which 0 being benign and 100 being a high risk. Example: 90
DstOriginalRiskLevel	Optional	Integer	The risk level associated with the destination, as reported by the reporting device. Example: Malicious
DstPortNumber	Optional	Integer	Destination Port number. Example: 53
DstHostname	Optional	String	The destination device hostname, excluding domain information. If no device name is available, store the relevant IP address in this field. Example: DESKTOP-1282V4D Note: This value is mandatory if DstIpAddr is specified.
DstDomain	Optional	String	The domain of the destination device. Example: Contoso
DstDomainType	Conditional	Enumerated	The type of DstDomain, if known. Possible values include: - Windows (contoso\mypc) - FQDN (learn.microsoft.com) Required if DstDomain is used.
DstFQDN	Optional	String	The destination device hostname, including domain information when available. Example: Contoso\DESKTOP-1282V4D Note: This field supports both traditional FQDN format and Windows domain\hostname format. The DstDomainType reflects the format used.
DstDvcId	Optional	String	The ID of the destination device as reported in the record. Example: ac7e9755-8eae-4ffc-8a02-50ed7a2216c3
DstDvcScopeId	Optional	String	The cloud platform scope ID the device belongs to. DstDvcScopeId map to a subscription ID on Azure and to an account ID on AWS.
DstDvcScope	Optional	String	The cloud platform scope the device belongs to. DstDvcScope map to a subscription ID on Azure and to an account ID on AWS.
DstDvcIdType	Conditional	Enumerated	The type of DstDvcId, if known. Possible values include: - AzureResourceId - MDEidIf If multiple IDs are available, use the first one from the list above, and store the others in the DstDvcAzureResourceId or DstDvcMDEid fields, respectively. Required if DstDeviceId is used.
DstDeviceType	Optional	Enumerated	The type of the destination device. Possible values include: - Computer - Mobile Device - IOT Device - Other
DstDescription	Optional	String	A descriptive text associated with the device. For example: Primary Domain Controller.

DNS specific fields

Field	Class	Type	Description
DnsQuery	Mandatory	String	The domain that the request tries to resolve. Notes: - Some sources send valid FQDN queries in a different format. For example, in the DNS protocol itself, the query includes a dot (.) at the end, which must be removed. - While the DNS protocol limits the type of value in this field to an FQDN, most DNS servers allow any value, and this field is therefore not limited to FQDN values only. Most notably, DNS tunneling attacks may use invalid FQDN values in the query field. - While the DNS protocol allows for multiple queries in a single request, this scenario is rare, if it's found at all. If the request has multiple queries, store the first one in this field, and then and optionally keep the rest in the AdditionalFields field. Example: www.malicious.com
Domain	Alias		Alias to DnsQuery.
DnsQueryType	Optional	Integer	The DNS Resource Record Type codes. Example: 28
DnsQueryTypeName	Recommended	Enumerated	The DNS Resource Record Type names. Notes: - IANA doesn't define the case for the values, so analytics must normalize the case as needed. - The value ANY is supported for the response code 255. - The value TYPExxxx is supported for unmapped response codes, where xxxx is the numerical value of the response code, as reported by the BIND DNS server. -If the source provides only a numerical query type code and not a query type name, the parser must include a lookup table to enrich with this value. Example: AAAA
DnsResponseName	Optional	String	The content of the response, as included in the record. The DNS response data is inconsistent across reporting devices, is complex to parse, and has less value for source-agnostic analytics. Therefore the information model doesn't require parsing and normalization, and Microsoft Sentinel uses an auxiliary function to provide response information. For more information, see Handling DNS response.
DnsResponseCodeName	Alias		Alias to EventResultDetails
DnsResponseCode	Optional	Integer	The DNS numerical response code. Example: 3
TransactionIdHex	Recommended	String	The DNS query unique ID as assigned by the DNS client, in hexadecimal format. Note that this value is part of the DNS protocol and different from DnsSessionId, the network layer session ID, typically assigned by the reporting device.
NetworkProtocol	Optional	Enumerated	The transport protocol used by the network resolution event. The value can be UDP or TCP, and is most commonly set to UDP for DNS. Example: UDP
NetworkProtocolVersion	Optional	Enumerated	The version of NetworkProtocol. When using it to distinguish between IP version, use the values IPv4 and IPv6.
DnsQueryClass	Optional	Integer	The DNS class ID. In practice, only the IN class (ID 1) is used, and therefore this field is less valuable.
DnsQueryClassName	Optional	String	The DNS class name. In practice, only the IN class (ID 1) is used, and therefore this field is less valuable. Example: IN
DnsFlags	Optional	String	The flags field, as provided by the reporting device. If flag information is provided in multiple fields, concatenate them with comma as a separator. Since DNS flags are complex to parse and are less often used by analytics, parsing, and normalization aren't required. Microsoft Sentinel can use an auxiliary function to provide flags information. For more information, see Handling DNS response. Example: ["DR"]
DnsNetworkDuration	Optional	Integer	The amount of time, in milliseconds, for the completion of DNS request. Example: 1500
Duration	Alias		Alias to DnsNetworkDuration
DnsFlagsAuthenticated	Optional	Boolean	The DNS AD flag, which is related to DNSSEC, indicates in a response that all data included in the answer and authority sections of the response have been verified by the server according to the policies of that server. For more information, see RFC 3655 Section 6.1 for more information.
DnsFlagsAuthoritative	Optional	Boolean	The DNS AA flag indicates whether the response from the server was authoritative
DnsFlagsCheckingDisabled	Optional	Boolean	The DNS CD flag, which is related to DNSSEC, indicates in a query that non-verified data is acceptable to the system sending the query. For more information, see RFC 3655 Section 6.1 for more information.
DnsFlagsRecursionAvailable	Optional	Boolean	The DNS RA flag indicates in a response that that server supports recursive queries.
DnsFlagsRecursionDesired	Optional	Boolean	The DNS RD flag indicates in a request that that client would like the server to use recursive queries.
DnsFlagsTruncated	Optional	Boolean	The DNS TC flag indicates that a response was truncated as it exceeded the maximum response size.
DnsFlagsZ	Optional	Boolean	The DNS Z flag is a deprecated DNS flag, which might be reported by older DNS systems.
DnsSessionId	Optional	string	The DNS session identifier as reported by the reporting device. This value is different from TransactionIdHex, the DNS query unique ID as assigned by the DNS client. Example: EB4BFA28-2EAD-4EF7-BC8A-51DF4FDF5B55
SessionId	Alias		Alias to DnsSessionId
DnsResponseIpCountry	Optional	Country	The country/region associated with one of the IP addresses in the DNS response. For more information, see Logical types. Example: USA
DnsResponseIpRegion	Optional	Region	The region, or state, associated with one of the IP addresses in the DNS response. For more information, see Logical types. Example: Vermont
DnsResponseIpCity	Optional	City	The city associated with one of the IP addresses in the DNS response. For more information, see Logical types. Example: Burlington
DnsResponseIpLatitude	Optional	Latitude	The latitude of the geographical coordinate associated with one of the IP addresses in the DNS response. For more information, see Logical types. Example: 44.475833
DnsResponseIpLongitude	Optional	Longitude	The longitude of the geographical coordinate associated with one of the IP addresses in the DNS response. For more information, see Logical types. Example: 73.211944

Inspection fields

The following fields are used to represent an inspection, which a DNS security device performed. The threat related fields represent a single threat that is associated with either the source address, the destination address, one of the IP addresses in the response or the DNS query domain. If more than one threat was identified as a threat, information about other IP addresses can be stored in the field AdditionalFields.

Field	Class	Type	Description
UrlCategory	Optional	String	A DNS event source may also look up the category of the requested Domains. The field is called UrlCategory to align with the Microsoft Sentinel network schema. DomainCategory is added as an alias that's fitting to DNS. Example: Educational \\ Phishing
DomainCategory	Alias		Alias to UrlCategory.
NetworkRuleName	Optional	String	The name or ID of the rule which identified the threat. Example: AnyAnyDrop
NetworkRuleNumber	Optional	Integer	The number of the rule which identified the threat. Example: 23
Rule	Alias	String	Either the value of NetworkRuleName or the value of NetworkRuleNumber. If the value of NetworkRuleNumber is used, the type should be converted to string.
ThreatId	Optional	String	The ID of the threat or malware identified in the network session. Example: Tr.124
ThreatCategory	Optional	String	If a DNS event source also provides DNS security, it may also evaluate the DNS event. For example, it can search for the IP address or domain in a threat intelligence database, and assign the domain or IP address with a Threat Category.
ThreatIpAddr	Optional	IP Address	An IP address for which a threat was identified. The field ThreatField contains the name of the field ThreatIpAddr represents. If a threat is identified in the Domain field, this field should be empty.
ThreatField	Conditional	Enumerated	The field for which a threat was identified. The value is either SrcIpAddr, DstIpAddr, Domain, or DnsResponseName.
ThreatName	Optional	String	The name of the threat identified, as reported by the reporting device.
ThreatConfidence	Optional	Integer	The confidence level of the threat identified, normalized to a value between 0 and a 100.
ThreatOriginalConfidence	Optional	String	The original confidence level of the threat identified, as reported by the reporting device.
ThreatRiskLevel	Optional	Integer	The risk level associated with the threat identified, normalized to a value between 0 and a 100.
ThreatOriginalRiskLevel	Optional	String	The original risk level associated with the threat identified, as reported by the reporting device.
ThreatIsActive	Optional	Boolean	True if the threat identified is considered an active threat.
ThreatFirstReportedTime	Optional	datetime	The first time the IP address or domain were identified as a threat.
ThreatLastReportedTime	Optional	datetime	The last time the IP address or domain were identified as a threat.

Deprecated aliases and fields

The following fields are aliases that are maintained for backwards compatibility. They were removed from the schema on December 31, 2021.

• Query (alias to DnsQuery)
• QueryType (alias to DnsQueryType)
• QueryTypeName (alias to DnsQueryTypeName)
• ResponseName (alias to DnsReasponseName)
• ResponseCodeName (alias to DnsResponseCodeName)
• ResponseCode (alias to DnsResponseCode)
• QueryClass (alias to DnsQueryClass)
• QueryClassName (alias to DnsQueryClassName)
• Flags (alias to DnsFlags)
• SrcUserDomain

Schema updates

The changes in version 0.1.2 of the schema are:

• Added the field EventSchema.
• Added dedicated flag field, which augments the combined Flags field: DnsFlagsAuthoritative, DnsFlagsCheckingDisabled, DnsFlagsRecursionAvailable, DnsFlagsRecursionDesired, DnsFlagsTruncated, and DnsFlagsZ.

The changes in version 0.1.3 of the schema are:

• The schema now explicitly documents Src*, Dst*, Process* and User* fields.
• Added more Dvc* fields to match the latest common fields definition.
• Added Src and Dst as aliases to a leading identifier for the source and destination systems.
• Added optional DnsNetworkDuration and Duration, an alias to it.
• Added optional Geo Location and Risk Level fields.

The changes in version 0.1.4 of the schema are:

• Added the optional fields ThreatIpAddr, ThreatField, ThreatName, ThreatConfidence, ThreatOriginalConfidence, ThreatOriginalRiskLevel, ThreatIsActive, ThreatFirstReportedTime, and ThreatLastReportedTime.

The changes in version 0.1.5 of the schema are:

• Added the fields SrcUserScope, SrcUserSessionId, SrcDvcScopeId, SrcDvcScope, DstDvcScopeId, DstDvcScope, DvcScopeId, and DvcScope.

The changes in version 0.1.6 of the schema are:

• Added the fields DnsResponseIpCountry, DnsResponseIpRegion, DnsResponseIpCity, DnsResponseIpLatitude, and DnsResponseIpLongitude.

The changes in version 0.1.7 of the schema are:

• Added the fields SrcDescription, SrcOriginalRiskLevel, DstDescription, DstOriginalRiskLevel, SrcUserScopeId, NetworkProtocolVersion, Rule, RuleName, RuleNumber, and ThreatId.

Source-specific discrepancies

The goal of normalizing is to ensure that all sources provide consistent telemetry. A source that doesn't provide the required telemetry, such as mandatory schema fields, cannot be normalized. However, sources that typically provide all required telemetry, even if there are some discrepancies, can be normalized. Discrepancies may affect the completeness of query results.

The following table lists known discrepancies:

Source	Discrepancies
Microsoft DNS Server Collected using the DNS connector and the Log Analytics Agent	The connector doesn't provide the mandatory DnsQuery field for original event ID 264 (Response to a dynamic update). The data is available at the source, but not forwarded by the connector.
Corelight Zeek	Corelight Zeek may not provide the mandatory DnsQuery field. We have observed such behavior in certain cases in which the DNS response code name is NXDOMAIN.

Handling DNS response

In most cases, logged DNS events don't include response information, which may be large and detailed. If your record includes more response information, store it in the ResponseName field as it appears in the record.

You can also provide an extra KQL function called _imDNS<vendor>Response_, which takes the unparsed response as input and returns dynamic value with the following structure:

[
    {
        "part": "answer"
        "query": "yahoo.com."
        "TTL": 1782
        "Class": "IN"
        "Type": "A"
        "Response": "74.6.231.21"
    }
    {
        "part": "authority"
        "query": "yahoo.com."
        "TTL": 113066
        "Class": "IN"
        "Type": "NS"
        "Response": "ns5.yahoo.com"
    }
    ...
]

The fields in each dictionary in the dynamic value correspond to the fields in each DNS response. The part entry should include either answer, authority, or additional to reflect the part in the response that the dictionary belongs to.

Tip

To ensure optimal performance, call the imDNS<vendor>Response function only when needed, and only after an initial filtering to ensure better performance.

Handling DNS flags

Parsing and normalization aren't required for flag data. Instead, store the flag data provided by the reporting device in the Flags field. If determining the value of individual flags is straight forward, you can also use the dedicated flags fields.

You can also provide an extra KQL function called _imDNS<vendor>Flags_, which takes the unparsed response, or dedicated flag fields, as input and returns a dynamic list, with Boolean values that represent each flag in the following order:

• Authenticated (AD)
• Authoritative (AA)
• Checking Disabled (CD)
• Recursion Available (RA)
• Recursion Desired (RD)
• Truncated (TC)
• Z

Next steps

For more information, see:

• Watch the ASIM Webinar or review the slides
• Advanced Security Information Model (ASIM) overview
• Advanced Security Information Model (ASIM) schemas
• Advanced Security Information Model (ASIM) parsers
• Advanced Security Information Model (ASIM) content