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

The Microsoft Sentinel Network Session normalization schema represents an IP network activity, such as network connections and network sessions. Such events are reported, for example, by operating systems, routers, firewalls, and intrusion prevention systems.

The network normalization schema can represent any type of an IP network session but is designed to provide support for common source types, such as Netflow, firewalls, and intrusion prevention systems.

For more information about normalization in Microsoft Sentinel, see Normalization and the Advanced Security Information Model (ASIM).

This article describes version 0.2.x of the network normalization schema. Version 0.1 was released before ASIM was available and doesn't align with ASIM in several places. For more information, see Differences between network normalization schema versions.

Important

The network normalization schema is currently in preview. This feature is provided without a service level agreement. We don't recommend it 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.

Parsers

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

Unifying 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 _Im_NetworkSession filtering parser or the _ASim_NetworkSession parameter-less parser.

You can also use workspace-deployed ImNetworkSession and ASimNetworkSession parsers by deploying them from the Microsoft Sentinel GitHub repository.

For more information, see built-in ASIM parsers and workspace-deployed parsers.

Out-of-the-box, source-specific parsers

For the list of the Network Session parsers Microsoft Sentinel provides out-of-the-box refer to the ASIM parsers list

Add your own normalized parsers

When developing custom parsers for the Network Session information model, name your KQL functions using the following syntax:

• vimNetworkSession<vendor><Product> for parametrized parsers
• ASimNetworkSession<vendor><Product> for regular parsers

Refer to the article Managing ASIM parsers to learn how to add your custom parsers to the network session unifying parsers.

Filtering parser parameters

The Network Session 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 network sessions that started at or after this time.
endtime	datetime	Filter only network sessions that started running at or before this time.
srcipaddr_has_any_prefix	dynamic	Filter only network sessions for which the source IP address field prefix is in one of the listed values. Prefixes should end with a ., for example: 10.0.. The length of the list is limited to 10,000 items.
dstipaddr_has_any_prefix	dynamic	Filter only network sessions for which the destination IP address field prefix is in one of the listed values. Prefixes should end with a ., for example: 10.0.. The length of the list is limited to 10,000 items.
ipaddr_has_any_prefix	dynamic	Filter only network sessions for which the destination IP address field or source IP address field prefix is in one of the listed values. Prefixes should end with a ., for example: 10.0.. The length of the list is limited to 10,000 items. The field ASimMatchingIpAddr is set with the one of the values SrcIpAddr, DstIpAddr, or Both to reflect the matching fields or fields.
dstportnumber	Int	Filter only network sessions with the specified destination port number.
hostname_has_any	dynamic/string	Filter only network sessions for which the destination hostname field has any of the values listed. The length of the list is limited to 10,000 items. The field ASimMatchingHostname is set with the one of the values SrcHostname, DstHostname, or Both to reflect the matching fields or fields.
dvcaction	dynamic/string	Filter only network sessions for which the Device Action field is any of the values listed.
eventresult	String	Filter only network sessions with a specific EventResult value.

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.'])

For example, to filter only network sessions for a specified list of domain names, use:

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

Tip

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 Network session security content.

Schema overview

The Network Session information model is aligned with the OSSEM Network entity schema.

The Network Session schema serves several types of similar but distinct scenarios, which share the same fields. Those scenarios are identified by the EventType field:

• NetworkSession - a network session reported by an intermediate device monitoring the network, such as a Firewall, a router, or a network tap.
• L2NetworkSession - a network sessions for which only layer 2 information is available. Such events will include MAC addresses but not IP addresses.
• Flow - an aggregated event that reports multiple similar network sessions, typically over a predefined time period, such as Netflow events.
• EndpointNetworkSession - a network session reported by one of the end points of the session, including clients and servers. For such events, the schema supports the remote and local alias fields.
• IDS - a network session reported as suspicious. Such an event will have some of the inspection fields populated, and may have just one IP address field populated, either the source or the destination.

Typically, a query should either select just a subset of those event types, and may need to address separately unique aspects of the use cases. For example, IDS events do not reflect the entire network volume and should not be taken into account in column based analytics.

Network session events use the descriptors Src and Dst to denote the roles of the devices and related users and applications involved in the session. So, for example, the source device hostname and IP address are named SrcHostname and SrcIpAddr. Other ASIM schemas typically use Target instead of Dst.

For events reported by an endpoint and for which the event type is EndpointNetworkSession, the descriptors Local and Remote denote the endpoint itself and the device at the other end of the network session respectively.

The descriptor Dvc is used for the reporting device, which is the local system for sessions reported by an endpoint, and the intermediary device or network tap for other network session events.

Schema details

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 Network Session events:

Field	Class	Type	Description
EventCount	Mandatory	Integer	Netflow sources support aggregation, and the EventCount field should be set to the value of the Netflow FLOWS field. For other sources, the value is typically set to 1.
EventType	Mandatory	Enumerated	Describes the scenario reported by the record. For Network Session records, the allowed values are: - EndpointNetworkSession - NetworkSession - L2NetworkSession - IDS - Flow For more information on event types, refer to the schema overview
EventSubType	Optional	String	Additional description of the event type, if applicable. For Network Session records, supported values include: - Start - End This is field is not relevant for Flow events.
EventResult	Mandatory	Enumerated	If the source device does not provide an event result, EventResult should be based on the value of DvcAction. If DvcAction is Deny, Drop, Drop ICMP, Reset, Reset Source, or Reset Destination , EventResult should be Failure. Otherwise, EventResult should be Success.
EventResultDetails	Recommended	Enumerated	Reason or details for the result reported in the EventResult field. Supported values are: - Failover - Invalid TCP - Invalid Tunnel - Maximum Retry - Reset - Routing issue - Simulation - Terminated - Timeout - Transient error - Unknown - NA. The original, source specific, value is stored in the EventOriginalResultDetails field.
EventSchema	Mandatory	String	The name of the schema documented here is NetworkSession.
EventSchemaVersion	Mandatory	String	The version of the schema. The version of the schema documented here is 0.2.6.
DvcAction	Recommended	Enumerated	The action taken on the network session. Supported values are: - Allow - Deny - Drop - Drop ICMP - Reset - Reset Source - Reset Destination - Encrypt - Decrypt - VPNroute Note: The value might be provided in the source record by using different terms, which should be normalized to these values. The original value should be stored in the DvcOriginalAction field. Example: drop
EventSeverity	Optional	Enumerated	If the source device does not provide an event severity, EventSeverity should be based on the value of DvcAction. If DvcAction is Deny, Drop, Drop ICMP, Reset, Reset Source, or Reset Destination , EventSeverity should be Low. Otherwise, EventSeverity should be Informational.
DvcInterface			The DvcInterface field should alias either the DvcInboundInterface or the DvcOutboundInterface fields.
Dvc fields			For Network Session events, device fields refer to the system reporting the Network Session 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 more information on each field, refer to 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

Network session fields

Field	Class	Type	Description
NetworkApplicationProtocol	Optional	String	The application layer protocol used by the connection or session. The value should be in all uppercase. Example: FTP
NetworkProtocol	Optional	Enumerated	The IP protocol used by the connection or session as listed in IANA protocol assignment, which is typically TCP, UDP, or ICMP. Example: TCP
NetworkProtocolVersion	Optional	Enumerated	The version of NetworkProtocol. When using it to distinguish between IP version, use the values IPv4 and IPv6.
NetworkDirection	Optional	Enumerated	The direction of the connection or session: - For the EventType NetworkSession, Flow or L2NetworkSession, NetworkDirection represents the direction relative to the organization or cloud environment boundary. Supported values are Inbound, Outbound, Local (to the organization), External (to the organization) or NA (Not Applicable). - For the EventType EndpointNetworkSession, NetworkDirection represents the direction relative to the endpoint. Supported values are Inbound, Outbound, Local (to the system), Listen or NA (Not Applicable). The Listen value indicates that a device has started accepting network connections but isn't actually, necessarily, connected.
NetworkDuration	Optional	Integer	The amount of time, in milliseconds, for the completion of the network session or connection. Example: 1500
Duration	Alias		Alias to NetworkDuration.
NetworkIcmpType	Optional	String	For an ICMP message, ICMP type name associated with the numerical value, as described in RFC 2780 for IPv4 network connections, or in RFC 4443 for IPv6 network connections. Example: Destination Unreachable for NetworkIcmpCode 3
NetworkIcmpCode	Optional	Integer	For an ICMP message, the ICMP code number as described in RFC 2780 for IPv4 network connections, or in RFC 4443 for IPv6 network connections.
NetworkConnectionHistory	Optional	String	TCP flags and other potential IP header information.
DstBytes	Recommended	Long	The number of bytes sent from the destination to the source for the connection or session. If the event is aggregated, DstBytes should be the sum over all aggregated sessions. Example: 32455
SrcBytes	Recommended	Long	The number of bytes sent from the source to the destination for the connection or session. If the event is aggregated, SrcBytes should be the sum over all aggregated sessions. Example: 46536
NetworkBytes	Optional	Long	Number of bytes sent in both directions. If both BytesReceived and BytesSent exist, BytesTotal should equal their sum. If the event is aggregated, NetworkBytes should be the sum over all aggregated sessions. Example: 78991
DstPackets	Optional	Long	The number of packets sent from the destination to the source for the connection or session. The meaning of a packet is defined by the reporting device. If the event is aggregated, DstPackets should be the sum over all aggregated sessions. Example: 446
SrcPackets	Optional	Long	The number of packets sent from the source to the destination for the connection or session. The meaning of a packet is defined by the reporting device. If the event is aggregated, SrcPackets should be the sum over all aggregated sessions. Example: 6478
NetworkPackets	Optional	Long	The number of packets sent in both directions. If both PacketsReceived and PacketsSent exist, BytesTotal should equal their sum. The meaning of a packet is defined by the reporting device. If the event is aggregated, NetworkPackets should be the sum over all aggregated sessions. Example: 6924
NetworkSessionId	Optional	string	The session identifier as reported by the reporting device. Example: 172\_12\_53\_32\_4322\_\_123\_64\_207\_1\_80
SessionId	Alias	String	Alias to NetworkSessionId.
TcpFlagsAck	Optional	Boolean	The TCP ACK Flag reported. The acknowledgment flag is used to acknowledge the successful receipt of a packet. As we can see from the diagram above, the receiver sends an ACK and a SYN in the second step of the three way handshake process to tell the sender that it received its initial packet.
TcpFlagsFin	Optional	Boolean	The TCP FIN Flag reported. The finished flag means there is no more data from the sender. Therefore, it is used in the last packet sent from the sender.
TcpFlagsSyn	Optional	Boolean	The TCP SYN Flag reported. The synchronization flag is used as a first step in establishing a three way handshake between two hosts. Only the first packet from both the sender and receiver should have this flag set.
TcpFlagsUrg	Optional	Boolean	The TCP URG Flag reported. The urgent flag is used to notify the receiver to process the urgent packets before processing all other packets. The receiver will be notified when all known urgent data has been received. See RFC 6093 for more details.
TcpFlagsPsh	Optional	Boolean	The TCP PSH Flag reported. The push flag is similar to the URG flag and tells the receiver to process these packets as they are received instead of buffering them.
TcpFlagsRst	Optional	Boolean	The TCP RST Flag reported. The reset flag gets sent from the receiver to the sender when a packet is sent to a particular host that was not expecting it.
TcpFlagsEce	Optional	Boolean	The TCP ECE Flag reported. This flag is responsible for indicating if the TCP peer is ECN capable. See RFC 3168 for more details.
TcpFlagsCwr	Optional	Boolean	The TCP CWR Flag reported. The congestion window reduced flag is used by the sending host to indicate it received a packet with the ECE flag set. See RFC 3168 for more details.
TcpFlagsNs	Optional	Boolean	The TCP NS Flag reported. The nonce sum flag is still an experimental flag used to help protect against accidental malicious concealment of packets from the sender. See RFC 3540 for more details

Destination system fields

Field	Class	Type	Description
Dst	Recommended	Alias	A unique identifier of the server receiving the DNS request. This field might alias the DstDvcId, DstHostname, or DstIpAddr fields. Example: 192.168.12.1
DstIpAddr	Recommended	IP address	The IP address of the connection or session destination. If the session uses network address translation, DstIpAddr is the publicly visible address, and not the original address of the source, which is stored in DstNatIpAddr Example: 2001:db8::ff00:42:8329 Note: This value is mandatory if DstHostname is specified.
DstPortNumber	Optional	Integer	The destination IP port. Example: 443
DstHostname	Recommended	Hostname	The destination device hostname, excluding domain information. If no device name is available, store the relevant IP address in this field. Example: DESKTOP-1282V4D
DstDomain	Recommended	String	The domain of the destination device. Example: Contoso
DstDomainType	Conditional	Enumerated	The type of DstDomain. For a list of allowed values and further information, refer to DomainType in the Schema Overview article. 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. If multiple IDs are available, use the most important one, and store the others in the fields DstDvc<DvcIdType>. 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. For a list of allowed values and further information, refer to DvcIdType in the Schema Overview article. Required if DstDeviceId is used.
DstDeviceType	Optional	Enumerated	The type of the destination device. For a list of allowed values and further information, refer to DeviceType in the Schema Overview article.
DstZone	Optional	String	The network zone of the destination, as defined by the reporting device. Example: Dmz
DstInterfaceName	Optional	String	The network interface used for the connection or session by the destination device. Example: Microsoft Hyper-V Network Adapter
DstInterfaceGuid	Optional	String	The GUID of the network interface used on the destination device. Example: 46ad544b-eaf0-47ef- 827c-266030f545a6
DstMacAddr	Optional	String	The MAC address of the network interface used for the connection or session by the destination device. Example: 06:10:9f:eb:8f:14
DstVlanId	Optional	String	The VLAN ID related to the destination device. Example: 130
OuterVlanId	Optional	Alias	Alias to DstVlanId. In many cases, the VLAN can't be determined as a source or a destination but is characterized as inner or outer. This alias to signifies that DstVlanId should be used when the VLAN is characterized as outer.
DstSubscriptionId	Optional	String	The cloud platform subscription ID the destination device belongs to. DstSubscriptionId map to a subscription ID on Azure and to an account ID on AWS.
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

Destination user fields

Field	Class	Type	Description
DstUserId	Optional	String	A machine-readable, alphanumeric, unique representation of the destination user. For the supported format for different ID types, refer to the User entity. Example: S-1-12
DstUserScope	Optional	String	The scope, such as Microsoft Entra tenant, in which DstUserId and DstUsername are defined. or more information and list of allowed values, see UserScope in the Schema Overview article.
DstUserScopeId	Optional	String	The scope ID, such as Microsoft Entra Directory ID, in which DstUserId and DstUsername are defined. for more information and list of allowed values, see UserScopeId in the Schema Overview article.
DstUserIdType	Conditional	UserIdType	The type of the ID stored in the DstUserId field. For a list of allowed values and further information, refer to UserIdType in the Schema Overview article.
DstUsername	Optional	String	The destination username, including domain information when available. For the supported format for different ID types, refer to the User entity. Use the simple form only if domain information isn't available. Store the Username type in the DstUsernameType field. If other username formats are available, store them in the fields DstUsername<UsernameType>. Example: AlbertE
User	Alias		Alias to DstUsername.
DstUsernameType	Conditional	UsernameType	Specifies the type of the username stored in the DstUsername field. For a list of allowed values and further information, refer to UsernameType in the Schema Overview article. Example: Windows
DstUserType	Optional	UserType	The type of destination user. For a list of allowed values and further information, refer to UserType in the Schema Overview article. Note: The value might be provided in the source record by using different terms, which should be normalized to these values. Store the original value in the DstOriginalUserType field.
DstOriginalUserType	Optional	String	The original destination user type, if provided by the source.

Destination application fields

Field	Class	Type	Description
DstAppName	Optional	String	The name of the destination application. Example: Facebook
DstAppId	Optional	String	The ID of the destination application, as reported by the reporting device.If DstAppType is Process, DstAppId and DstProcessId should have the same value. Example: 124
DstAppType	Optional	AppType	The type of the destination application. For a list of allowed values and further information, refer to AppType in the Schema Overview article. This field is mandatory if DstAppName or DstAppId are used.
DstProcessName	Optional	String	The file name of the process that terminated the network session. This name is typically considered to be the process name. Example: C:\Windows\explorer.exe
Process	Alias		Alias to the DstProcessName Example: C:\Windows\System32\rundll32.exe
DstProcessId	Optional	String	The process ID (PID) of the process that terminated the network session. 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.
DstProcessGuid	Optional	String	A generated unique identifier (GUID) of the process that terminated the network session. Example: EF3BD0BD-2B74-60C5-AF5C-010000001E00

Source system fields

Field	Class	Type	Description
Src	Alias		A unique identifier of the source device. This field might alias the SrcDvcId, SrcHostname, or SrcIpAddr fields. Example: 192.168.12.1
SrcIpAddr	Recommended	IP address	The IP address from which the connection or session originated. This value is mandatory if SrcHostname is specified. If the session uses network address translation, SrcIpAddr is the publicly visible address, and not the original address of the source, which is stored in SrcNatIpAddr Example: 77.138.103.108
SrcPortNumber	Optional	Integer	The IP port from which the connection originated. Might not be relevant for a session comprising multiple connections. Example: 2335
SrcHostname	Recommended	Hostname	The source device hostname, excluding domain information. If no device name is available, store the relevant IP address in this field. Example: DESKTOP-1282V4D
SrcDomain	Recommended	String	The domain of the source device. Example: Contoso
SrcDomainType	Conditional	DomainType	The type of SrcDomain. For a list of allowed values and further information, refer to DomainType in the Schema Overview article. 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. If multiple IDs are available, use the most important one, and store the others in the fields SrcDvc<DvcIdType>. 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	DvcIdType	The type of SrcDvcId. For a list of allowed values and further information, refer to DvcIdType in the Schema Overview article. Note: This field is required if SrcDvcId is used.
SrcDeviceType	Optional	DeviceType	The type of the source device. For a list of allowed values and further information, refer to DeviceType in the Schema Overview article.
SrcZone	Optional	String	The network zone of the source, as defined by the reporting device. Example: Internet
SrcInterfaceName	Optional	String	The network interface used for the connection or session by the source device. Example: eth01
SrcInterfaceGuid	Optional	String	The GUID of the network interface used on the source device. Example: 46ad544b-eaf0-47ef- 827c-266030f545a6
SrcMacAddr	Optional	String	The MAC address of the network interface from which the connection or session originated. Example: 06:10:9f:eb:8f:14
SrcVlanId	Optional	String	The VLAN ID related to the source device. Example: 130
InnerVlanId	Optional	Alias	Alias to SrcVlanId. In many cases, the VLAN can't be determined as a source or a destination but is characterized as inner or outer. This alias to signifies that SrcVlanId should be used when the VLAN is characterized as inner.
SrcSubscriptionId	Optional	String	The cloud platform subscription ID the source device belongs to. SrcSubscriptionId map to a subscription ID on Azure and to an account ID on AWS.
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

Source user fields

Field	Class	Type	Description
SrcUserId	Optional	String	A machine-readable, alphanumeric, unique representation of the source user. For the supported format for different ID types, refer to the User entity. Example: S-1-12
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 a list of allowed values and further information, refer to UserIdType in the Schema Overview article.
SrcUsername	Optional	String	The source username, including domain information when available. For the supported format for different ID types, refer to the User entity. Use the simple form only if domain information isn't available. Store the Username type in the SrcUsernameType field. If other username formats are available, store them in the fields SrcUsername<UsernameType>. Example: AlbertE
SrcUsernameType	Conditional	UsernameType	Specifies the type of the username stored in the SrcUsername field. For a list of allowed values and further information, refer to UsernameType in the Schema Overview article. Example: Windows
SrcUserType	Optional	UserType	The type of source user. For a list of allowed values and further information, refer to UserType in the Schema Overview article. Note: The value might be provided in the source record by using different terms, which should be normalized to these values. Store the original value in the SrcOriginalUserType field.
SrcOriginalUserType	Optional	String	The original destination user type, if provided by the reporting device.

Source application fields

Field	Class	Type	Description
SrcAppName	Optional	String	The name of the source application. Example: filezilla.exe
SrcAppId	Optional	String	The ID of the source application, as reported by the reporting device. If SrcAppType is Process, SrcAppId and SrcProcessId should have the same value. Example: 124
SrcAppType	Optional	AppType	The type of the source application. For a list of allowed values and further information, refer to AppType in the Schema Overview article. This field is mandatory if SrcAppName or SrcAppId are used.
SrcProcessName	Optional	String	The file name of the process that initiated the network session. This name is typically considered to be the process name. Example: C:\Windows\explorer.exe
SrcProcessId	Optional	String	The process ID (PID) of the process that initiated the network session. 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 network session. Example: EF3BD0BD-2B74-60C5-AF5C-010000001E00

Local and remote aliases

All the source and destination fields listed above, can be optionally aliased by fields with the same name and the descriptors Local and Remote. This is typically helpful for events reported by an endpoint and for which the event type is EndpointNetworkSession.

For such events the descriptors Local and Remote denote the endpoint itself and the device at the other end of the network session respectively. For inbound connections, the local system is the destination, Local fields are aliases to the Dst fields, and 'Remote' fields are aliases to Src fields. Conversely, for outbound connections, the local system is the source, Local fields are aliases to the Src fields, and Remote fields are aliases to Dst fields.

For example, for an inbound event, the field LocalIpAddr is an alias to DstIpAddr and the field RemoteIpAddr is an alias to SrcIpAddr.

Hostname and IP address aliases

Field	Class	Type	Description
Hostname	Alias		- If the event type is NetworkSession, Flow or L2NetworkSession, Hostname is an alias to DstHostname. - If the event type is EndpointNetworkSession, Hostname is an alias to RemoteHostname, which can alias either DstHostname or SrcHostName, depending on NetworkDirection
IpAddr	Alias		- If the event type is NetworkSession, Flow or L2NetworkSession, IpAddr is an alias to SrcIpAddr. - If the event type is EndpointNetworkSession, IpAddr is an alias to LocalIpAddr, which can alias either SrcIpAddr or DstIpAddr, depending on NetworkDirection.

Intermediary device and Network Address Translation (NAT) fields

The following fields are useful if the record includes information about an intermediary device, such as a firewall or a proxy, which relays the network session.

Intermediary systems often use address translation and therefore the original address and the address observed externally are not the same. In such cases, the primary address fields such as SrcIPAddr and DstIpAddr represent the addresses observed externally, while the NAT address fields, SrcNatIpAddr and DstNatIpAddr represent the internal address of the original device before translation.

Field	Class	Type	Description
DstNatIpAddr	Optional	IP address	The DstNatIpAddr represents either of: - The original address of the destination device if network address translation was used. - The IP address used by the intermediary device for communication with the source. Example: 2::1
DstNatPortNumber	Optional	Integer	If reported by an intermediary NAT device, the port used by the NAT device for communication with the source. Example: 443
SrcNatIpAddr	Optional	IP address	The SrcNatIpAddr represents either of: - The original address of the source device if network address translation was used. - The IP address used by the intermediary device for communication with the destination. Example: 4.3.2.1
SrcNatPortNumber	Optional	Integer	If reported by an intermediary NAT device, the port used by the NAT device for communication with the destination. Example: 345
DvcInboundInterface	Optional	String	If reported by an intermediary device, the network interface used by the NAT device for the connection to the source device. Example: eth0
DvcOutboundInterface	Optional	String	If reported by an intermediary device, the network interface used by the NAT device for the connection to the destination device. Example: Ethernet adapter Ethernet 4e

Inspection fields

The following fields are used to represent that inspection which a security device such as a firewall, an IPS, or a web security gateway performed:

Field	Class	Type	Description
NetworkRuleName	Optional	String	The name or ID of the rule by which DvcAction was decided upon. Example: AnyAnyDrop
NetworkRuleNumber	Optional	Integer	The number of the rule by which DvcAction was decided upon. 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
ThreatName	Optional	String	The name of the threat or malware identified in the network session. Example: EICAR Test File
ThreatCategory	Optional	String	The category of the threat or malware identified in the network session. Example: Trojan
ThreatRiskLevel	Optional	Integer	The risk level associated with the session. The level should be a number between 0 and 100. Note: The value might be provided in the source record by using a different scale, which should be normalized to this scale. The original value should be stored in ThreatRiskLevelOriginal.
ThreatOriginalRiskLevel	Optional	String	The risk level as reported by the reporting device.
ThreatIpAddr	Optional	IP Address	An IP address for which a threat was identified. The field ThreatField contains the name of the field ThreatIpAddr represents.
ThreatField	Conditional	Enumerated	The field for which a threat was identified. The value is either SrcIpAddr or DstIpAddr.
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.
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.

Other fields

If the event is reported by one of the endpoints of the network session, it might include information about the process that initiated or terminated the session. In such cases, the ASIM Process Event schema is used to normalize this information.

Schema updates

The following are the changes in version 0.2.1 of the schema:

• Added Src and Dst as aliases to a leading identifier for the source and destination systems.
• Added the fields NetworkConnectionHistory, SrcVlanId, DstVlanId, InnerVlanId, and OuterVlanId.

The following are the changes in version 0.2.2 of the schema:

• Added Remote and Local aliases.
• Added the event type EndpointNetworkSession.
• Defined Hostname and IpAddr as aliases for RemoteHostname and LocalIpAddr respectively when the event type is EndpointNetworkSession.
• Defined DvcInterface as an alias to DvcInboundInterface or DvcOutboundInterface.
• Changed the type of the following fields from Integer to Long: SrcBytes, DstBytes, NetworkBytes, SrcPackets, DstPackets, and NetworkPackets.
• Added the fields NetworkProtocolVersion, SrcSubscriptionId, and DstSubscriptionId.
• Deprecated DstUserDomain and SrcUserDomain.

The following are the changes in version 0.2.3 of the schema:

• Added the ipaddr_has_any_prefix filtering parameter.
• The hostname_has_any filtering parameter now matches either source or destination hostnames.
• Added the fields ASimMatchingHostname and ASimMatchingIpAddr.

The following are the changes in version 0.2.4 of the schema:

• Added the TcpFlags fields.
• Updated NetworkIcpmType and NetworkIcmpCode to reflect the number value for both.
• Added additional inspection fields.
• The field 'ThreatRiskLevelOriginal' was renamed to ThreatOriginalRiskLevel to align with ASIM conventions. Existing Microsoft parsers will maintain ThreatRiskLevelOriginal until May 1st 2023.
• Marked EventResultDetails as recommended, and specified the allowed values.

The following are the changes in version 0.2.5 of the schema:

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

The following are the changes in version 0.2.6 of the schema:

• Added IDS as an event type

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