TI map Email entity to OfficeActivity

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

'Identifies a match in OfficeActivity table from any Email IOC from TI'

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566` Phishing

Rule body kusto

id: 795d43a3-6edc-4c99-971f-00d05841e5ac
name: TI map Email entity to OfficeActivity
description: |
  'Identifies a match in OfficeActivity table from any Email IOC from TI'
severity: Medium
requiredDataConnectors:
  - connectorId: Office365
    dataTypes:
      - OfficeActivity
  - connectorId: ThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: ThreatIntelligenceTaxii
    dataTypes:
      - ThreatIntelIndicators
  - connectorId: MicrosoftDefenderThreatIntelligence
    dataTypes:
      - ThreatIntelIndicators
queryFrequency: 1h
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1566
query: |
  let dt_lookBack = 1h;
  let ioc_lookBack = 14d;
  let emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$';
  let OfficeEvents = materialize(
    OfficeActivity
    | where isnotempty(UserId)
    | where TimeGenerated >= ago(dt_lookBack)
    | where UserId matches regex emailregex
    | project-rename  OfficeActivity_TimeGenerated = TimeGenerated);
  let OfficeActivityUPNs = OfficeEvents | distinct UserId = tolower(UserId) | summarize make_list(UserId);
  ThreatIntelIndicators
  | extend IndicatorType = replace(@"\[|\]|\""", "", tostring(split(ObservableKey, ":", 0)))
  | where IndicatorType == "email-addr"
  | extend EmailSenderAddress = ObservableValue
  | extend EmailSourceDomain = substring(EmailSenderAddress, indexof(EmailSenderAddress, "@") + 1, strlen(EmailSenderAddress) - indexof(EmailSenderAddress, "@") - 1)
  | extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
  | extend Url = iff(ObservableKey == "url:value", ObservableValue, "")
  | where TimeGenerated >= ago(ioc_lookBack) 
  | where tolower(EmailSenderAddress) in (OfficeActivityUPNs)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by Id, ObservableValue
  | where IsActive and (ValidUntil > now() or isempty(ValidUntil))
  | extend Description = tostring(parse_json(Data).description)
  | where Description !contains_cs "State: inactive;" and Description !contains_cs "State: falsepos;"
  | project-reorder *, TrafficLightProtocolLevel, EmailSenderAddress, EmailSourceDomain, 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 (OfficeEvents) on $left.EmailSenderAddress == $right.UserId
  | where OfficeActivity_TimeGenerated < ValidUntil
  | summarize OfficeActivity_TimeGenerated = arg_max(OfficeActivity_TimeGenerated, *) by Id, UserId
  | extend Description = tostring(parse_json(Data).description)
  | extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))
  | project OfficeActivity_TimeGenerated, Description, ActivityGroupNames, Id, ValidUntil, Confidence, EmailSenderAddress, EmailSourceDomain, UserId, ClientIP, Operation, UserType, RecordType, OfficeWorkload, Parameters, Url
  | extend Name = tostring(split(UserId, '@', 0)[0]), UPNSuffix = tostring(split(UserId, '@', 1)[0])
  | extend timestamp = OfficeActivity_TimeGenerated
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: UserId
      - identifier: Name
        columnName: Name
      - identifier: UPNSuffix
        columnName: UPNSuffix
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: ClientIP
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: Url
version: 1.2.11
kind: Scheduled

Stages and Predicates

Parameters

let dt_lookBack = 1h;
let ioc_lookBack = 14d;
let emailregex = @'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$';

Let binding: `OfficeEvents`

let OfficeEvents = materialize(
  OfficeActivity
  | where isnotempty(UserId)
  | where TimeGenerated >= ago(dt_lookBack)
  | where UserId matches regex emailregex
  | project-rename  OfficeActivity_TimeGenerated = TimeGenerated);

Derived from dt_lookBack, emailregex.

Let binding: `OfficeActivityUPNs`

let OfficeActivityUPNs = OfficeEvents | distinct UserId = tolower(UserId) | summarize make_list(UserId);

Derived from OfficeEvents.

Stage 1: `source`

ThreatIntelIndicators

Stage 2: `extend`

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

Stage 3: `where`

| where IndicatorType == "email-addr"

Stage 4: `extend` (4 consecutive steps)

| extend EmailSenderAddress = ObservableValue
| extend EmailSourceDomain = substring(EmailSenderAddress, indexof(EmailSenderAddress, "@") + 1, strlen(EmailSenderAddress) - indexof(EmailSenderAddress, "@") - 1)
| extend TrafficLightProtocolLevel = tostring(parse_json(AdditionalFields).TLPLevel)
| extend Url = iff(ObservableKey == "url:value", ObservableValue, "")

Stage 5: `where`

| where TimeGenerated >= ago(ioc_lookBack)

Stage 6: `where`

| where tolower(EmailSenderAddress) in (OfficeActivityUPNs)

References OfficeActivityUPNs (defined above).

Stage 7: `summarize`

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

Stage 8: `where`

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

Stage 9: `extend`

| extend Description = tostring(parse_json(Data).description)

Stage 10: `where`

| where Description !contains_cs "State: inactive;" and Description !contains_cs "State: falsepos;"

Stage 11: `project-reorder`

| project-reorder *, TrafficLightProtocolLevel, EmailSenderAddress, EmailSourceDomain, Type

Stage 12: `join`

| join kind=innerunique (OfficeEvents) on $left.EmailSenderAddress == $right.UserId

Stage 13: `where`

| where OfficeActivity_TimeGenerated < ValidUntil

Stage 14: `summarize`

| summarize OfficeActivity_TimeGenerated = arg_max(OfficeActivity_TimeGenerated, *) by Id, UserId

Stage 15: `extend`

| extend Description = tostring(parse_json(Data).description)

Stage 16: `extend`

| extend ActivityGroupNames = extract(@"ActivityGroup:(\S+)", 1, tostring(parse_json(Data).labels))

Stage 17: `project`

| project OfficeActivity_TimeGenerated, Description, ActivityGroupNames, Id, ValidUntil, Confidence, EmailSenderAddress, EmailSourceDomain, UserId, ClientIP, Operation, UserType, RecordType, OfficeWorkload, Parameters, Url

Stage 18: `extend`

| extend Name = tostring(split(UserId, '@', 0)[0]), UPNSuffix = tostring(split(UserId, '@', 1)[0])

Stage 19: `extend`

| extend timestamp = OfficeActivity_TimeGenerated

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`Description`	contains	`State: falsepos;`
`Description`	contains	`State: inactive;`

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
`EmailSenderAddress`	in	`OfficeActivityUPNs` transforms: `tolower`, `cased`
`IndicatorType`	eq	`email-addr` transforms: `cased`
`OfficeActivity_TimeGenerated`	lt	`ValidUntil` transforms: `cased`
`UserId`	is_not_null	(no value, null check)
`UserId`	regex_match	`^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+.[a-zA-Z0-9-.]+$`
`ValidUntil`	is_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`
`ClientIP`	`project`
`Confidence`	`project`
`Description`	`project`
`EmailSenderAddress`	`project`
`EmailSourceDomain`	`project`
`Id`	`project`
`OfficeActivity_TimeGenerated`	`project`
`OfficeWorkload`	`project`
`Operation`	`project`
`Parameters`	`project`
`RecordType`	`project`
`Url`	`project`
`UserId`	`project`
`UserType`	`project`
`ValidUntil`	`project`
`Name`	`extend`
`UPNSuffix`	`extend`
`timestamp`	`extend`

`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 Email entity to OfficeActivity

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `OfficeEvents`

Let binding: `OfficeActivityUPNs`

Stage 1: `source`

Stage 2: `extend`

Stage 3: `where`

Stage 4: `extend` (4 consecutive steps)

Stage 5: `where`

Stage 6: `where`

Stage 7: `summarize`

Stage 8: `where`

Stage 9: `extend`

Stage 10: `where`

Stage 11: `project-reorder`

Stage 12: `join`

Stage 13: `where`

Stage 14: `summarize`

Stage 15: `extend`

Stage 16: `extend`

Stage 17: `project`

Stage 18: `extend`

Stage 19: `extend`

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

TI map Email entity to OfficeActivity

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: OfficeEvents

Let binding: OfficeActivityUPNs

Stage 1: source

Stage 2: extend

Stage 3: where

Stage 4: extend (4 consecutive steps)

Stage 5: where

Stage 6: where

Stage 7: summarize

Stage 8: where

Stage 9: extend

Stage 10: where

Stage 11: project-reorder

Stage 12: join

Stage 13: where

Stage 14: summarize

Stage 15: extend

Stage 16: extend

Stage 17: project

Stage 18: extend

Stage 19: extend

Exclusions

Indicators

Output fields

Let binding: `OfficeEvents`

Let binding: `OfficeActivityUPNs`

Stage 1: `source`

Stage 2: `extend`

Stage 3: `where`

Stage 4: `extend` (4 consecutive steps)

Stage 5: `where`

Stage 6: `where`

Stage 7: `summarize`

Stage 8: `where`

Stage 9: `extend`

Stage 10: `where`

Stage 11: `project-reorder`

Stage 12: `join`

Stage 13: `where`

Stage 14: `summarize`

Stage 15: `extend`

Stage 16: `extend`

Stage 17: `project`

Stage 18: `extend`

Stage 19: `extend`