Red Sift - Email with URL to previously unseen domain

Status: available
Severity: medium
Time window: 14d
Group by: CorrelationUid, DstHostname, EmailFrom, EmailMessageUid, EmailReturnPath, EmailSubject, Message, Severity, SrcIp, TimeGenerated
Source: github.com/Azure/Azure-Sentinel

'Detects email forensics events containing one or more URLs whose domain has not been seen in the previous 14 days, which may indicate newly observed phishing infrastructure or suspicious delivery patterns.'

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566` Phishing

Rule body kusto

id: 8972b513-12a2-4b46-8263-3f091d88a8bc
name: Red Sift - Email with URL to previously unseen domain
description: |
  'Detects email forensics events containing one or more URLs whose domain has not been seen in the previous 14 days, which may indicate newly observed phishing infrastructure or suspicious delivery patterns.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: RedSiftPush
    dataTypes:
      - RedSiftEmailForensics_CL
queryFrequency: 1h
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1566
query: |
  let lookback = 14d;
  let recentWindow = 1h;
  let historicalDomains = RedSiftEmailForensics_CL
  | extend EmailUrls = todynamic(EmailUrls)
  | where TimeGenerated between (ago(lookback) .. ago(recentWindow))
  | where isnotempty(EmailUrls) and array_length(EmailUrls) > 0
  | mv-expand Url = EmailUrls
  | extend UrlString = tostring(Url.url_string)
  | where isnotempty(UrlString)
  | extend UrlDomain = tostring(parse_url(UrlString).Host)
  | where isnotempty(UrlDomain)
  | summarize by UrlDomain;
  RedSiftEmailForensics_CL
  | extend
      EmailFrom = tostring(column_ifexists("EmailFrom", "")),
      EmailSubject = tostring(column_ifexists("EmailSubject", "")),
      EmailReturnPath = tostring(column_ifexists("EmailReturnPath", "")),
      EmailMessageUid = tostring(column_ifexists("EmailMessageUid", "")),
      SrcIp = tostring(column_ifexists("SrcIp", "")),
      DstHostname = tostring(column_ifexists("DstHostname", "")),
      Severity = tostring(column_ifexists("Severity", "")),
      Message = tostring(column_ifexists("Message", "")),
      CorrelationUid = tostring(column_ifexists("CorrelationUid", "")),
      EmailUrls = todynamic(EmailUrls)
  | where TimeGenerated >= ago(recentWindow)
  | where isnotempty(EmailUrls) and array_length(EmailUrls) > 0
  | mv-expand Url = EmailUrls
  | extend UrlString = tostring(Url.url_string)
  | where isnotempty(UrlString)
  | extend UrlDomain = tostring(parse_url(UrlString).Host)
  | where isnotempty(UrlDomain)
  | join kind=leftanti (historicalDomains) on UrlDomain
  | summarize
      NewUrlDomains = make_set(UrlDomain, 50),
      NewUrls = make_set(UrlString, 50),
      NewDomainCount = dcount(UrlDomain),
      UrlCount = dcount(UrlString),
      RepresentativeUrlDomain = take_any(UrlDomain)
      by TimeGenerated,
      EmailFrom,
      EmailSubject,
      EmailReturnPath,
      EmailMessageUid,
      SrcIp,
      DstHostname,
      Severity,
      Message,
      CorrelationUid
  | extend
      NewUrlDomainList = strcat_array(NewUrlDomains, ", "),
      NewUrlList = strcat_array(NewUrls, ", ")
  | project
      TimeGenerated,
      EmailFrom,
      EmailSubject,
      EmailReturnPath,
      EmailMessageUid,
      SrcIp,
      DstHostname,
      RepresentativeUrlDomain,
      NewDomainCount,
      UrlCount,
      NewUrlDomainList,
      NewUrlList,
      Severity,
      Message,
      CorrelationUid
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: EmailFrom
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIp
  - entityType: DNS
    fieldMappings:
      - identifier: DomainName
        columnName: RepresentativeUrlDomain
customDetails:
  EmailSubject: EmailSubject
  ReturnPath: EmailReturnPath
  NewDomainCount: NewDomainCount
  NewUrlDomainList: NewUrlDomainList
  NewUrlList: NewUrlList
  CorrelationUid: CorrelationUid
alertDetailsOverride:
  alertDisplayNameFormat: "RedSift - URL to new domain in email from {{EmailFrom}}"
  alertDescriptionFormat: "Email from {{EmailFrom}} contains {{NewDomainCount}} previously unseen URL domain(s): {{NewUrlDomainList}}."
incidentConfiguration:
  createIncident: true
  groupingConfiguration:
    enabled: true
    reopenClosedIncident: false
    lookbackDuration: P1D
    matchingMethod: Selected
    groupByEntities:
      - Account
      - DNS
    groupByCustomDetails:
      - EmailSubject
eventGroupingSettings:
  aggregationKind: AlertPerResult
suppressionEnabled: false
suppressionDuration: PT1H
version: 1.0.0
kind: Scheduled

Stages and Predicates

Parameters

let lookback = 14d;
let recentWindow = 1h;

Let binding: `historicalDomains`

let historicalDomains = RedSiftEmailForensics_CL
| extend EmailUrls = todynamic(EmailUrls)
| where TimeGenerated between (ago(lookback) .. ago(recentWindow))
| where isnotempty(EmailUrls) and array_length(EmailUrls) > 0
| mv-expand Url = EmailUrls
| extend UrlString = tostring(Url.url_string)
| where isnotempty(UrlString)
| extend UrlDomain = tostring(parse_url(UrlString).Host)
| where isnotempty(UrlDomain)
| summarize by UrlDomain;

Derived from lookback, recentWindow.

Stage 1: `source`

RedSiftEmailForensics_CL

Stage 2: `extend`

| extend
    EmailFrom = tostring(column_ifexists("EmailFrom", "")),
    EmailSubject = tostring(column_ifexists("EmailSubject", "")),
    EmailReturnPath = tostring(column_ifexists("EmailReturnPath", "")),
    EmailMessageUid = tostring(column_ifexists("EmailMessageUid", "")),
    SrcIp = tostring(column_ifexists("SrcIp", "")),
    DstHostname = tostring(column_ifexists("DstHostname", "")),
    Severity = tostring(column_ifexists("Severity", "")),
    Message = tostring(column_ifexists("Message", "")),
    CorrelationUid = tostring(column_ifexists("CorrelationUid", "")),
    EmailUrls = todynamic(EmailUrls)

Stage 3: `where`

| where TimeGenerated >= ago(recentWindow)

Stage 4: `where`

| where isnotempty(EmailUrls) and array_length(EmailUrls) > 0

Stage 5: `mv-expand`

| mv-expand Url = EmailUrls

Stage 6: `extend`

| extend UrlString = tostring(Url.url_string)

Stage 7: `where`

| where isnotempty(UrlString)

Stage 8: `extend`

| extend UrlDomain = tostring(parse_url(UrlString).Host)

Stage 9: `where`

| where isnotempty(UrlDomain)

Stage 10: `join` (negated)

| join kind=leftanti (historicalDomains) on UrlDomain

Stage 11: `summarize`

| summarize
    NewUrlDomains = make_set(UrlDomain, 50),
    NewUrls = make_set(UrlString, 50),
    NewDomainCount = dcount(UrlDomain),
    UrlCount = dcount(UrlString),
    RepresentativeUrlDomain = take_any(UrlDomain)
    by TimeGenerated,
    EmailFrom,
    EmailSubject,
    EmailReturnPath,
    EmailMessageUid,
    SrcIp,
    DstHostname,
    Severity,
    Message,
    CorrelationUid

Stage 12: `extend`

| extend
    NewUrlDomainList = strcat_array(NewUrlDomains, ", "),
    NewUrlList = strcat_array(NewUrls, ", ")

Stage 13: `project`

| project
    TimeGenerated,
    EmailFrom,
    EmailSubject,
    EmailReturnPath,
    EmailMessageUid,
    SrcIp,
    DstHostname,
    RepresentativeUrlDomain,
    NewDomainCount,
    UrlCount,
    NewUrlDomainList,
    NewUrlList,
    Severity,
    Message,
    CorrelationUid

Exclusions

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

Field	Kind	Excluded values
`EmailUrls`	gt	`0`
`EmailUrls`	is_not_null	(no value, null check)
`UrlDomain`	is_not_null	(no value, null check)
`UrlString`	is_not_null	(no value, null check)

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
`EmailUrls`	gt	`0` transforms: `array_length`
`EmailUrls`	is_not_null	(no value, null check)
`UrlDomain`	is_not_null	(no value, null check)
`UrlString`	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
`CorrelationUid`	`project`
`DstHostname`	`project`
`EmailFrom`	`project`
`EmailMessageUid`	`project`
`EmailReturnPath`	`project`
`EmailSubject`	`project`
`Message`	`project`
`NewDomainCount`	`project`
`NewUrlDomainList`	`project`
`NewUrlList`	`project`
`RepresentativeUrlDomain`	`project`
`Severity`	`project`
`SrcIp`	`project`
`TimeGenerated`	`project`
`UrlCount`	`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)

Red Sift - Email with URL to previously unseen domain

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `historicalDomains`

Stage 1: `source`

Stage 2: `extend`

Stage 3: `where`

Stage 4: `where`

Stage 5: `mv-expand`

Stage 6: `extend`

Stage 7: `where`

Stage 8: `extend`

Stage 9: `where`

Stage 10: `join` (negated)

Stage 11: `summarize`

Stage 12: `extend`

Stage 13: `project`

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Red Sift - Email with URL to previously unseen domain

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: historicalDomains

Stage 1: source

Stage 2: extend

Stage 3: where

Stage 4: where

Stage 5: mv-expand

Stage 6: extend

Stage 7: where

Stage 8: extend

Stage 9: where

Stage 10: join (negated)

Stage 11: summarize

Stage 12: extend

Stage 13: project

Exclusions

Indicators

Output fields

Let binding: `historicalDomains`

Stage 1: `source`

Stage 2: `extend`

Stage 3: `where`

Stage 4: `where`

Stage 5: `mv-expand`

Stage 6: `extend`

Stage 7: `where`

Stage 8: `extend`

Stage 9: `where`

Stage 10: `join` (negated)

Stage 11: `summarize`

Stage 12: `extend`

Stage 13: `project`