Detection rules › Kusto

CYFIRMA - Attack Surface - Cloud Weakness Medium Rule

This is a third-party alert feed, not a detection over modeled telemetry. The vendor product raised the finding; this rule forwards it into the SIEM. It is searchable for reference but is excluded from the detection-rule browse and the ATT&CK coverage matrix.

Status: available
Severity: medium
Time window: 5m
Source: github.com/Azure/Azure-Sentinel

"This rule detects cloud storage buckets (e.g., AWS S3) that are publicly accessible without authentication. Such misconfigurations can lead to data exfiltration, compliance violations, and reputational damage. The detection is based on Cyfirma's Attack Surface Intelligence."

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1087.004` Account Discovery: Cloud Account

Rule body kusto

id: b8a3c5e2-04d5-4b61-9b62-b4f53a417f74 
name: CYFIRMA - Attack Surface - Cloud Weakness Medium Rule
description: |
  "This rule detects cloud storage buckets (e.g., AWS S3) that are publicly accessible without authentication. 
  Such misconfigurations can lead to data exfiltration, compliance violations, and reputational damage. 
  The detection is based on Cyfirma's Attack Surface Intelligence."
version: 1.0.1
kind: Scheduled
severity: Medium
requiredDataConnectors:
  - connectorId: CyfirmaAttackSurfaceAlertsConnector
    dataTypes:
      - CyfirmaASCloudWeaknessAlerts_CL
queryFrequency: 5m
queryPeriod: 5m
triggerOperator: gt
triggerThreshold: 0
status: Available
tactics:
  - InitialAccess
  - Collection
  - Discovery
  - Exfiltration
relevantTechniques:
  - T1087
  - T1087.004
query: |
  // Medium Severity - Attack Surface - Cloud Weakness - Unauthorized Public Cloud Storage Exposure Detected
  let timeFrame = 5m;
  CyfirmaASCloudWeaknessAlerts_CL
  | where severity == 'High' and TimeGenerated between (ago(timeFrame) .. now())
  | extend
      Description=description,
      FirstSeen=first_seen,
      LastSeen=last_seen,
      RiskScore=risk_score,
      Domain=asset_name,
      AlertUID=alert_uid,
      UID=uid,
      Source=source,
      SourceType=source_type,
      CreatedDate=created_date,
      Impact=impact,
      ProviderName='CYFIRMA',
      ProductName='DeCYFIR/DeTCT'
  | project
      TimeGenerated,
      Description,
      Domain,
      RiskScore,
      FirstSeen,
      LastSeen,
      AlertUID,
      UID,
      Source,
      SourceType,
      CreatedDate,
      Impact,
      ProviderName,
      ProductName
entityMappings:
  - entityType: DNS
    fieldMappings:
      - identifier: DomainName
        columnName: Domain
customDetails:
  TimeGenerated: TimeGenerated
  RiskScore: RiskScore
  FirstSeen: FirstSeen
  LastSeen: LastSeen
  AlertUID: AlertUID
  UID: UID
  Source: Source
  SourceType: SourceType
  CreatedDate: CreatedDate
  Impact: Impact
alertDetailsOverride:
  alertDisplayNameFormat: "CYFIRMA - Medium Severity Alert - Unauthorized Public Cloud Storage Exposure Detected - Domain: {{Domain}}"
  alertDescriptionFormat: "CYFIRMA - Medium Severity Alert - Unauthorized Public Cloud Storage Exposure Detected - {{Description}}"
  alertDynamicProperties:
    - alertProperty: ProductName
      value: ProductName
    - alertProperty: ProviderName
      value: ProviderName
incidentConfiguration:
  createIncident: true
  groupingConfiguration:
    enabled: false
    reopenClosedIncident: false
    lookbackDuration: PT5H
    matchingMethod: AllEntities
eventGroupingSettings:
  aggregationKind: AlertPerResult

Stages and Predicates

Parameters

let timeFrame = 5m;

Stage 1: `source`

CyfirmaASCloudWeaknessAlerts_CL

Stage 2: `where`

| where severity == 'High' and TimeGenerated between (ago(timeFrame) .. now())

Stage 3: `extend`

| extend
    Description=description,
    FirstSeen=first_seen,
    LastSeen=last_seen,
    RiskScore=risk_score,
    Domain=asset_name,
    AlertUID=alert_uid,
    UID=uid,
    Source=source,
    SourceType=source_type,
    CreatedDate=created_date,
    Impact=impact,
    ProviderName='CYFIRMA',
    ProductName='DeCYFIR/DeTCT'

Stage 4: `project`

| project
    TimeGenerated,
    Description,
    Domain,
    RiskScore,
    FirstSeen,
    LastSeen,
    AlertUID,
    UID,
    Source,
    SourceType,
    CreatedDate,
    Impact,
    ProviderName,
    ProductName

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
`severity`	eq	`High` transforms: `cased`

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
`AlertUID`	`project`
`CreatedDate`	`project`
`Description`	`project`
`Domain`	`project`
`FirstSeen`	`project`
`Impact`	`project`
`LastSeen`	`project`
`ProductName`	`project`
`ProviderName`	`project`
`RiskScore`	`project`
`Source`	`project`
`SourceType`	`project`
`TimeGenerated`	`project`
`UID`	`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)

CYFIRMA - Attack Surface - Cloud Weakness Medium Rule

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `project`

Indicators

Output fields

Keyboard shortcuts

Search operators

CYFIRMA - Attack Surface - Cloud Weakness Medium Rule

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: extend

Stage 4: project

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `extend`

Stage 4: `project`