Cisco SEG - Suspicious sender domain

Status: available
Severity: medium
Time window: 1h
Source: github.com/Azure/Azure-Sentinel

'Detects suspicious sender domain age.'

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566` Phishing

Rule body kusto

id: ef0a253c-95b5-48e1-8ebc-dbeb073b9338
name: Cisco SEG - Suspicious sender domain
description: |
  'Detects suspicious sender domain age.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: CefAma
    dataTypes:
      - CommonSecurityLog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1566
query: |
  CiscoSEGEvent
  | where NetworkDirection =~ 'Incoming'
  | extend rec_domain = extract(@'@(.*)', 1, DstUserName)
  | extend s_domain = extract(@'@(.*)', 1, SrcUserName)
  | where s_domain != rec_domain
  | where tostring(AdditionalFields) has 'ESASDRDomainAge'
  | extend domain_age = extract(@'ESASDRDomainAge":"(.*days)"', 1, tostring(AdditionalFields))
  | extend yy = toint(extract(@'(\d+)\syears', 1, domain_age))
  | extend mm = toint(extract(@'(\d+)\smonths', 1, domain_age))
  | extend dd = toint(extract(@'(\d+)\sdays', 1, domain_age))
  | where isempty(yy)
  | where isempty(mm) or mm <= 2
  | extend AccountCustomEntity = SrcUserName
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: Name
        columnName: AccountCustomEntity
version: 1.0.3
kind: Scheduled

Stages and Predicates

Stage 1: `source`

CiscoSEGEvent

Stage 2: `where`

| where NetworkDirection =~ 'Incoming'

Stage 3: `extend`

| extend rec_domain = extract(@'@(.*)', 1, DstUserName)

Stage 4: `extend`

| extend s_domain = extract(@'@(.*)', 1, SrcUserName)

Stage 5: `where`

| where s_domain != rec_domain

Stage 6: `where`

| where tostring(AdditionalFields) has 'ESASDRDomainAge'

Stage 7: `extend` (4 consecutive steps)

| extend domain_age = extract(@'ESASDRDomainAge":"(.*days)"', 1, tostring(AdditionalFields))
| extend yy = toint(extract(@'(\d+)\syears', 1, domain_age))
| extend mm = toint(extract(@'(\d+)\smonths', 1, domain_age))
| extend dd = toint(extract(@'(\d+)\sdays', 1, domain_age))

Stage 8: `where`

| where isempty(yy)

Stage 9: `where`

| where isempty(mm) or mm <= 2

Stage 10: `extend`

| extend AccountCustomEntity = SrcUserName

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
`AdditionalFields`	match	`ESASDRDomainAge` transforms: `tostring`, `term`
`NetworkDirection`	eq	`Incoming`
`mm`	is_null	(no value, null check)
`mm`	le	`2` transforms: `cased`
`s_domain`	ne	`rec_domain` transforms: `cased`
`yy`	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
`rec_domain`	`extend`
`s_domain`	`extend`
`domain_age`	`extend`
`yy`	`extend`
`mm`	`extend`
`dd`	`extend`
`AccountCustomEntity`	`extend`

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`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
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`↑` / `↓`	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)

Cisco SEG - Suspicious sender domain

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `where`

Stage 7: `extend` (4 consecutive steps)

Stage 8: `where`

Stage 9: `where`

Stage 10: `extend`

Indicators

Output fields

Keyboard shortcuts

Search operators

Cisco SEG - Suspicious sender domain

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Stage 1: source

Stage 2: where

Stage 3: extend

Stage 4: extend

Stage 5: where

Stage 6: where

Stage 7: extend (4 consecutive steps)

Stage 8: where

Stage 9: where

Stage 10: extend

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `extend`

Stage 5: `where`

Stage 6: `where`

Stage 7: `extend` (4 consecutive steps)

Stage 8: `where`

Stage 9: `where`

Stage 10: `extend`