TI map Domain entity to Web Session Events (ASIM Web Session schema)

Severity: medium
Time window: 14d
Group by: DomainName, Id, IndicatorId, ObservableValue, domain
Source: github.com/Azure/Azure-Sentinel

'This rule identifies Web Sessions for which the target URL hostname is a known IoC. This rule uses the Advanced Security Information Model (ASIM) and supports any web session source that complies with ASIM.'

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1071` Application Layer Protocol

Rule body kusto

id: afa4cb9e-6fec-4742-a17f-f494b54c01e7
name: TI map Domain entity to Web Session Events (ASIM Web Session schema)
description: |
  'This rule identifies Web Sessions for which the target URL hostname is a known IoC. This rule uses the [Advanced Security Information Model (ASIM)](https:/aka.ms/AboutASIM) and supports any web session source that complies with ASIM.'
severity: Medium
requiredDataConnectors:
  - connectorId: SquidProxy
    dataTypes:
      - SquidProxy_CL
  - connectorId: Zscaler
    dataTypes:
      - CommonSecurityLog
  - connectorId: ThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: ThreatIntelligenceTaxii
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: MicrosoftDefenderThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
queryFrequency: 1h
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
relevantTechniques:
  - T1071
query: |
    let HAS_ANY_MAX = 10000;
    let dt_lookBack = 1h;
    let ioc_lookBack = 14d;
    //Create a list of TLDs in our threat feed for later validation
    let DOMAIN_TI=ThreatIntelIndicators
    // Picking up only IOC's that contain the entities we want
    | extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))
    | where IndicatorType == "domain-name"
    | extend DomainName = tolower(ObservableValue)
    | extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
    | extend IndicatorId = tostring(split(Id, "--")[2])
    | extend Url = iff(ObservableKey == "url:value", ObservableValue, "")
    | where TimeGenerated >= ago(ioc_lookBack)
    | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue
    | where IsActive and (ValidUntil > now() or isempty(ValidUntil));
    let DOMAIN_TI_list= todynamic(toscalar(DOMAIN_TI | summarize NIoCs = dcount(DomainName), Domains = make_set(DomainName) 
      | project Domains=iff(NIoCs > HAS_ANY_MAX, dynamic([]), Domains) ));
    DOMAIN_TI
    | project-reorder *, IsActive, Tags, TrafficLightProtocolLevel, DomainName, Type
    // using innerunique to keep perf fast and result set low, we only need one match to indicate potential malicious activity that needs to be investigated
    | join kind=innerunique (
        _Im_WebSession(starttime=ago(dt_lookBack), url_has_any= DOMAIN_TI_list )
        //Extract domain patterns from syslog message
        | extend domain = tostring(parse_url(Url)["Host"])
        | where isnotempty(domain)
        | extend tld = tostring(split(domain, '.')[-1])
        | extend Event_TimeGenerated = TimeGenerated
    ) on $left.DomainName==$right.domain
    | where Event_TimeGenerated < ValidUntil
    | summarize Event_TimeGenerated  = arg_max(Event_TimeGenerated , *) by IndicatorId, domain
    | extend Description = tostring(parse_json(Data).description)
    | extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
    | extend ThreatType = tostring(Data.indicator_types[0])
    | project Event_TimeGenerated, Description, ActivityGroupNames, IndicatorId, ValidUntil, Confidence, domain, SrcIpAddr, Url, ThreatType
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
customDetails:
  EventTime: Event_TimeGenerated
  IoCDescription: Description
  ActivityGroupNames: ActivityGroupNames
  IndicatorId: IndicatorId
  ThreatType: ThreatType
  IoCExpirationTime: ValidUntil
  IoCConfidenceScore: Confidence
alertDetailsOverride:
  alertDisplayNameFormat: A web request from {{SrcIpAddr}} to hostname  {{domain}} matched an IoC
  alertDescriptionFormat: A client with address {{SrcIpAddr}} requested the URL {{Url}}, whose hostname is a known indicator of compromise of {{ThreatType}}. Consult the threat intelligence blade for more information on the indicator.
version: 1.0.11
kind: Scheduled

Stages and Predicates

Parameters

let HAS_ANY_MAX = 10000;
let dt_lookBack = 1h;
let ioc_lookBack = 14d;

Let binding: `DOMAIN_TI_list`

let DOMAIN_TI_list = todynamic(toscalar(DOMAIN_TI | summarize NIoCs = dcount(DomainName), Domains = make_set(DomainName) 
  | project Domains=iff(NIoCs > HAS_ANY_MAX, dynamic([]), Domains) ));

Derived from HAS_ANY_MAX, DOMAIN_TI.

The stages below define let DOMAIN_TI (the rule's main pipeline source).

Stage 1: `source`

ThreatIntelIndicators

Stage 2: `extend`

| extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))

Stage 3: `where`

| where IndicatorType == "domain-name"

Stage 4: `extend` (4 consecutive steps)

| extend DomainName = tolower(ObservableValue)
| extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
| extend IndicatorId = tostring(split(Id, "--")[2])
| extend Url = iff(ObservableKey == "url:value", ObservableValue, "")

Stage 5: `where`

| where TimeGenerated >= ago(ioc_lookBack)

Stage 6: `summarize`

| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue

Stage 7: `where`

| where IsActive and (ValidUntil > now() or isempty(ValidUntil))

The stages below run on DOMAIN_TI (the outer pipeline).

Stage 8: `project-reorder`

DOMAIN_TI
| project-reorder *, IsActive, Tags, TrafficLightProtocolLevel, DomainName, Type

Stage 9: `join`

| join kind=innerunique (
    _Im_WebSession(starttime=ago(dt_lookBack), url_has_any= DOMAIN_TI_list )
    | extend domain = tostring(parse_url(Url)["Host"])
    | where isnotempty(domain)
    | extend tld = tostring(split(domain, '.')[-1])
    | extend Event_TimeGenerated = TimeGenerated
) on $left.DomainName==$right.domain

Stage 10: `where`

| where Event_TimeGenerated < ValidUntil

Stage 11: `summarize`

| summarize Event_TimeGenerated  = arg_max(Event_TimeGenerated , *) by IndicatorId, domain

Stage 12: `extend` (3 consecutive steps)

| extend Description = tostring(parse_json(Data).description)
| extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
| extend ThreatType = tostring(Data.indicator_types[0])

Stage 13: `project`

| project Event_TimeGenerated, Description, ActivityGroupNames, IndicatorId, ValidUntil, Confidence, domain, SrcIpAddr, Url, ThreatType

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`Event_TimeGenerated`	lt	`ValidUntil` transforms: `cased`
`IndicatorType`	eq	`domain-name` transforms: `cased`
`ValidUntil`	is_null	(no value, null check)
`domain`	is_not_null	(no value, null check)

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`ActivityGroupNames`	`project`
`Confidence`	`project`
`Description`	`project`
`Event_TimeGenerated`	`project`
`IndicatorId`	`project`
`SrcIpAddr`	`project`
`ThreatType`	`project`
`Url`	`project`
`ValidUntil`	`project`
`domain`	`project`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

TI map Domain entity to Web Session Events (ASIM Web Session schema)

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `DOMAIN_TI_list`

Stage 1: `source`

Stage 2: `extend`

Stage 3: `where`

Stage 4: `extend` (4 consecutive steps)

Stage 5: `where`

Stage 6: `summarize`

Stage 7: `where`

Stage 8: `project-reorder`

Stage 9: `join`

Stage 10: `where`

Stage 11: `summarize`

Stage 12: `extend` (3 consecutive steps)

Stage 13: `project`

Indicators

Output fields

Keyboard shortcuts

Search operators

TI map Domain entity to Web Session Events (ASIM Web Session schema)

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: DOMAIN_TI_list

Stage 1: source

Stage 2: extend

Stage 3: where

Stage 4: extend (4 consecutive steps)

Stage 5: where

Stage 6: summarize

Stage 7: where

Stage 8: project-reorder

Stage 9: join

Stage 10: where

Stage 11: summarize

Stage 12: extend (3 consecutive steps)

Stage 13: project

Indicators

Output fields

Let binding: `DOMAIN_TI_list`

Stage 1: `source`

Stage 2: `extend`

Stage 3: `where`

Stage 4: `extend` (4 consecutive steps)

Stage 5: `where`

Stage 6: `summarize`

Stage 7: `where`

Stage 8: `project-reorder`

Stage 9: `join`

Stage 10: `where`

Stage 11: `summarize`

Stage 12: `extend` (3 consecutive steps)

Stage 13: `project`