Brute force attack against user credentials (Uses Authentication Normalization)

Severity: medium
Time window: 20m
Group by: TargetUserId, TargetUserType, TargetUsername
Author: Ofer Shezaf
Source: github.com/Azure/Azure-Sentinel

Identifies evidence of brute force activity against a user based on multiple authentication failures and at least one successful authentication within a given time window. Note that the query does not enforce any sequence, and does not require the successful authentication to occur last. The default failure threshold is 10, success threshold is 1, and the default time window is 20 minutes. To use this analytics rule, make sure you have deployed the ASIM normalization parsers

MITRE ATT&CK coverage

Tactic	Techniques
Credential Access	`T1110` Brute Force

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 4624	An account was successfully logged on.
Security-Auditing	Event ID 4625	An account failed to log on.
Security-Auditing	Event ID 4634	An account was logged off.

Rule body kusto

id: a6c435a2-b1a0-466d-b730-9f8af69262e8
name: Brute force attack against user credentials (Uses Authentication Normalization)
description: |
  'Identifies evidence of brute force activity against a user based on multiple authentication failures and at least one successful authentication within a given time window.
  Note that the query does not enforce any sequence, and does not require the successful authentication to occur last.
  The default failure threshold is 10, success threshold is 1, and the default time window is 20 minutes.
  To use this analytics rule, make sure you have deployed the [ASIM normalization parsers](https://aka.ms/ASimAuthentication)'
severity: Medium
requiredDataConnectors: []
queryFrequency: 20m
queryPeriod: 20m
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CredentialAccess
relevantTechniques:
  - T1110
tags:
  - Id: 28b42356-45af-40a6-a0b4-a554cdfd5d8a
    version: 1.0.0
  - Schema: ASIMAuthentication
    SchemaVersion: 0.1.0
query: |
  let failureCountThreshold = 10;
  let successCountThreshold = 1;
  // let authenticationWindow = 20m; // Implicit in the analytic rule query period 
  imAuthentication
  | where TargetUserType != "NonInteractive"
  | summarize 
        StartTime = min(TimeGenerated), 
        EndTime = max(TimeGenerated), 
        IpAddresses = make_set (SrcDvcIpAddr, 100),
        ReportedBy = make_set (strcat (EventVendor, "/", EventProduct), 100),
        FailureCount = countif(EventResult=='Failure'),
        SuccessCount = countif(EventResult=='Success')
    by 
        TargetUserId, TargetUsername, TargetUserType 
  | where FailureCount >= failureCountThreshold and SuccessCount >= successCountThreshold
  | extend
        IpAddresses = strcat_array(IpAddresses, ", "), 
        ReportedBy = strcat_array(ReportedBy, ", ")
  | extend
    Name = iif(
        TargetUsername contains "@"
            , tostring(split(TargetUsername, '@', 0)[0])
            , TargetUsername
        ),
    UPNSuffix = iif(
        TargetUsername contains "@"
        , tostring(split(TargetUsername, '@', 1)[0])
        , ""
    )
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: TargetUserName
      - identifier: Name
        columnName: Name
      - identifier: UPNSuffix
        columnName: UPNSuffix

customDetails:
  IpAddresses: IpAddresses
  ReportedBy: ReportedBy
version: 1.2.5
kind: Scheduled
metadata:
    source:
        kind: Community
    author:
        name: Ofer Shezaf
    support:
        tier: Community
    categories:
        domains: [ "Security - Others", "Identity" ]

Stages and Predicates

Parameters

let failureCountThreshold = 10;
let successCountThreshold = 1;

Stage 1: `source`

imAuthentication

Stage 2: `where`

| where TargetUserType != "NonInteractive"

Stage 3: `summarize`

| summarize 
      StartTime = min(TimeGenerated), 
      EndTime = max(TimeGenerated), 
      IpAddresses = make_set (SrcDvcIpAddr, 100),
      ReportedBy = make_set (strcat (EventVendor, "/", EventProduct), 100),
      FailureCount = countif(EventResult=='Failure'),
      SuccessCount = countif(EventResult=='Success')
  by 
      TargetUserId, TargetUsername, TargetUserType

Threshold: ge 10

Stage 4: `where`

| where FailureCount >= failureCountThreshold and SuccessCount >= successCountThreshold

Stage 5: `extend`

| extend
      IpAddresses = strcat_array(IpAddresses, ", "), 
      ReportedBy = strcat_array(ReportedBy, ", ")

Stage 6: `extend`

| extend
  Name = iif(
      TargetUsername contains "@"
          , tostring(split(TargetUsername, '@', 0)[0])
          , TargetUsername
      ),
  UPNSuffix = iif(
      TargetUsername contains "@"
      , tostring(split(TargetUsername, '@', 1)[0])
      , ""
  )

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
`FailureCount`	ge	`10` transforms: `cased` corpus 2 (kusto 2)
`SuccessCount`	ge	`1` transforms: `cased` corpus 2 (kusto 2)
`TargetUserType`	ne	`NonInteractive` 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
`EndTime`	`summarize`
`FailureCount`	`summarize`
`IpAddresses`	`extend`
`ReportedBy`	`extend`
`StartTime`	`summarize`
`SuccessCount`	`summarize`
`TargetUserId`	`summarize`
`TargetUserType`	`summarize`
`TargetUsername`	`summarize`
`Name`	`extend`
`UPNSuffix`	`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)

Brute force attack against user credentials (Uses Authentication Normalization)

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: `source`

Stage 2: `where`

Stage 3: `summarize`

Stage 4: `where`

Stage 5: `extend`

Stage 6: `extend`

Indicators

Output fields

Keyboard shortcuts

Search operators

Brute force attack against user credentials (Uses Authentication Normalization)

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: summarize

Stage 4: where

Stage 5: extend

Stage 6: extend

Indicators

Output fields

Stage 1: `source`

Stage 2: `where`

Stage 3: `summarize`

Stage 4: `where`

Stage 5: `extend`

Stage 6: `extend`