Critical or High Severity Detections by User

Status: available
Severity: high
Time window: 1h
Group by: DstHostName, DstUserName, FileHash, FileName, Message, SrcIpAddr
Source: github.com/Azure/Azure-Sentinel

'Creates an incident when a large number of Critical or High severity CrowdStrike Falcon sensor detections is triggered by a single user within 1 hour. The rule uses the CrowdStrikeFalconEventStream table, filters for DetectionSummaryEvent records with Severity set to Critical or High, and alerts when detections for a single DstUserName exceed the configured threshold of 15. Review DstHostName, SrcIpAddr, FileName, FileHash, and Message for investigation context.'

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1562` Impair Defenses
Impact	`T1489` Service Stop

Rule body kusto

id: 4465ebde-b381-45f7-ad08-7d818070a11c
name: Critical or High Severity Detections by User
description: |
  'Creates an incident when a large number of Critical or High severity CrowdStrike Falcon sensor detections is triggered by a single user within 1 hour. The rule uses the CrowdStrikeFalconEventStream table, filters for DetectionSummaryEvent records with Severity set to Critical or High, and alerts when detections for a single DstUserName exceed the configured threshold of 15. Review DstHostName, SrcIpAddr, FileName, FileHash, and Message for investigation context.'
severity: High
status: Available
requiredDataConnectors:
  - connectorId: CefAma
    dataTypes:
      - CommonSecurityLog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics: 
- Impact
- DefenseEvasion
relevantTechniques:
- T1489
- T1562
query: |
  let timeframe = 1h;
  let threshold = 15; // update threshold value based on organization's preference
  let NotableEvents = CrowdStrikeFalconEventStream
  | where TimeGenerated > ago(timeframe)
  | where EventType == "DetectionSummaryEvent"
  | where Severity in ("Critical", "High")
  | summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), Total = count() by DstUserName, DstHostName, SrcIpAddr, FileName, FileHash, Message
  | where Total > threshold;
  NotableEvents
  | extend timestamp = StartTimeUtc, AccountCustomEntity = DstUserName, HostCustomEntity = DstHostName, IPCustomEntity = SrcIpAddr, FileHashCustomEntity = FileHash, FileHashAlgo = "MD5"
  | project timestamp, StartTimeUtc, EndTimeUtc, DstUserName, DstHostName, SrcIpAddr, FileName, FileHash, FileHashAlgo, Message, Total, AccountCustomEntity, HostCustomEntity, IPCustomEntity, FileHashCustomEntity
entityMappings:
- entityType: Account
  fieldMappings:
  - identifier: FullName
    columnName: AccountCustomEntity
- entityType: Host
  fieldMappings:
  - identifier: FullName
    columnName: HostCustomEntity
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: IPCustomEntity
- entityType: FileHash
  fieldMappings:
  - identifier: Algorithm
    columnName: FileHashAlgo
  - identifier: Value
    columnName: FileHashCustomEntity
alertDetailsOverride:
  alertDisplayNameFormat: 'CrowdStrike critical/high detections by user: {{DstUserName}}'
  alertDescriptionFormat: User {{DstUserName}} generated {{Total}} critical/high detections from host {{DstHostName}}.
customDetails:
  DstUserName: DstUserName
  DstHostName: DstHostName
  SrcIpAddr: SrcIpAddr
  FileName: FileName
  FileHash: FileHash
  Total: Total
version: 1.0.5
kind: Scheduled

Stages and Predicates

Parameters

let timeframe = 1h;
let threshold = 15;

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

Stage 1: `source`

CrowdStrikeFalconEventStream

Stage 2: `where`

| where TimeGenerated > ago(timeframe)

Stage 3: `where`

| where EventType == "DetectionSummaryEvent"

Stage 4: `where`

| where Severity in ("Critical", "High")

Stage 5: `summarize`

| summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), Total = count() by DstUserName, DstHostName, SrcIpAddr, FileName, FileHash, Message

Threshold: gt 15

Stage 6: `where`

| where Total > threshold

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

Stage 7: `extend`

NotableEvents
| extend timestamp = StartTimeUtc, AccountCustomEntity = DstUserName, HostCustomEntity = DstHostName, IPCustomEntity = SrcIpAddr, FileHashCustomEntity = FileHash, FileHashAlgo = "MD5"

Stage 8: `project`

| project timestamp, StartTimeUtc, EndTimeUtc, DstUserName, DstHostName, SrcIpAddr, FileName, FileHash, FileHashAlgo, Message, Total, AccountCustomEntity, HostCustomEntity, IPCustomEntity, FileHashCustomEntity

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
`EventType`	eq	`DetectionSummaryEvent` transforms: `cased`
`Severity`	in	`Critical` transforms: `cased` `High` transforms: `cased`
`Total`	gt	`15` 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
`AccountCustomEntity`	`project`
`DstHostName`	`project`
`DstUserName`	`project`
`EndTimeUtc`	`project`
`FileHash`	`project`
`FileHashAlgo`	`project`
`FileHashCustomEntity`	`project`
`FileName`	`project`
`HostCustomEntity`	`project`
`IPCustomEntity`	`project`
`Message`	`project`
`SrcIpAddr`	`project`
`StartTimeUtc`	`project`
`Total`	`project`
`timestamp`	`project`

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`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)

Critical or High Severity Detections by User

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `summarize`

Stage 6: `where`

Stage 7: `extend`

Stage 8: `project`

Indicators

Output fields

Keyboard shortcuts

Search operators

Critical or High Severity Detections by User

MITRE ATT&CK coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: summarize

Stage 6: where

Stage 7: extend

Stage 8: project

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `summarize`

Stage 6: `where`

Stage 7: `extend`

Stage 8: `project`