KQL Search

id: e3f4a5b6-c7d8-4e9f-0a1b-2c3d4e5f6a7b
name: "SigninLogs — Credential Stuffing Attack (High-Velocity Invalid Credentials)"
version: 1.0.0
kind: Scheduled
description: |
  Detects credential stuffing attacks: a single IP generating 50 or more ResultType 50126 errors (invalid username or password) against multiple accounts. Attackers use credential lists from previous data breaches. MITRE ATT&CK: T1110.004 (Credential Stuffing).
severity: High
requiredDataConnectors:
  - connectorId: AzureActiveDirectory
    dataTypes:
      - SigninLogs
queryFrequency: PT6H
queryPeriod: P7D
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CredentialAccess
relevantTechniques:
  - T1110
query: |

    // ---- Network Allowlist (exclude trusted IPs / CIDR / ranges) --------------
    let _allow = materialize(union isfuzzy=true (print R="" | take 0), (_GetWatchlist('NetworkAllowlist') | project R = tostring(IPOrRange)) | where isnotempty(R));
    let _allowCIDR  = toscalar(_allow | where not(R matches regex @'^\d+\.\d+\.\d+\.\d+-\d+\.\d+\.\d+\.\d+$') | extend R = iff(R has '/', R, strcat(R, '/32')) | summarize make_list(R));
    let _allowRange = toscalar(_allow | where R matches regex @'^\d+\.\d+\.\d+\.\d+-\d+\.\d+\.\d+\.\d+$' | summarize make_list(R));
    let _ExcludeAllowlistedIPs = (T:(IPAddress:string)) {
        T
        | extend IPAddress = tostring(IPAddress)
        | where array_length(_allowCIDR) == 0 or isnull(ipv4_is_in_any_range(IPAddress, _allowCIDR)) or not(ipv4_is_in_any_range(IPAddress, _allowCIDR))
        | mv-apply _r = _allowRange to typeof(string) on (
            extend _lo = tostring(split(_r,'-')[0]), _hi = tostring(split(_r,'-')[1])
            | extend _inRange = ipv4_compare(IPAddress, _lo) >= 0 and ipv4_compare(IPAddress, _hi) <= 0
            | summarize _anyInRange = max(toint(_inRange)))
        | where isnull(_anyInRange) or _anyInRange == 0
        | project-away _anyInRange
    };
    // ---------------------------------------------------------------------------
    let velocityThreshold = 50;
    SigninLogs
    | invoke _ExcludeAllowlistedIPs()
    | where TimeGenerated > ago(7d)
    | where ResultType == "50126"
    | summarize
        InvalidCredAttempts = count(),
        UniqueUsers         = dcount(UserPrincipalName),
        Users               = make_set(UserPrincipalName, 50),
        StartTime           = min(TimeGenerated),
        EndTime             = max(TimeGenerated),
        Locations           = make_set(Location, 5)
      by IPAddress
    | where InvalidCredAttempts >= velocityThreshold
    | project
        TimeGenerated = StartTime,
        IPAddress, InvalidCredAttempts, UniqueUsers,
        Users, EndTime, Locations
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IPAddress
customDetails:
  InvalidCredAttempts: InvalidCredAttempts
  UniqueUsers: UniqueUsers
alertDetailsOverride:
  alertDisplayNameFormat: "Credential Stuffing from {{IPAddress}} — {{InvalidCredAttempts}} attempts"
  alertDescriptionFormat: "{{UniqueUsers}} accounts targeted with invalid credentials (50126) from {{IPAddress}} over 7 days."
incidentConfiguration:
  createIncident: true
  groupingConfiguration:
    enabled: true
    reopenClosedIncident: false
    lookbackDuration: PT1H
    matchingMethod: AllEntities
    groupByEntities:
  - IP