SecurityEvent - Multiple authentication failures followed by a success

id: cf3ede88-a429-493b-9108-3e46d3c741f7
name: SecurityEvent - Multiple authentication failures followed by a success
description: |
  'Identifies accounts who have failed to logon to the domain multiple times in a row, followed by a successful authentication within a short time frame. Multiple failed attempts followed by a success can be an indication of a brute force attempt or possible mis-configuration of a service account within an environment.
  The lookback is set to 2h and the authentication window and threshold are set to 1h and 5, meaning we need to see a minimum of 5 failures followed by a success for an account within 1 hour to surface an alert.'
severity: Low
requiredDataConnectors:
  - connectorId: SecurityEvents
    dataTypes:
      - SecurityEvent
  - connectorId: WindowsSecurityEvents
    dataTypes:
      - SecurityEvent
queryFrequency: 2h
queryPeriod: 2h
triggerOperator: gt
triggerThreshold: 0
status: Available
tactics:
  - CredentialAccess
relevantTechniques:
  - T1110
query: |
    let timeRange = 2h;
    let authenticationWindow = 1h;
    let authenticationThreshold = 5;
    SecurityEvent
    | where TimeGenerated > ago(timeRange)
    | where EventID in (4624, 4625)
    | where IpAddress != "-" and isnotempty(Account)
    | extend Outcome = iff(EventID == 4624, "Success", "Failure")
    // bin outcomes into 10 minute windows to reduce the volume of data
    | summarize OutcomeCount=count() by bin(TimeGenerated, 10m), Account, IpAddress, Computer, Outcome
    | project TimeGenerated, Account, IpAddress, Computer, Outcome, OutcomeCount
    // sort ready for sessionizing - by account and time of the authentication outcome
    | sort by TimeGenerated asc, Account, IpAddress, Computer, Outcome, OutcomeCount
    | serialize
    // sessionize into failure groupings until either the account changes or there is a success
    | extend SessionStartedUtc = row_window_session(TimeGenerated, timeRange, authenticationWindow, Account != prev(Account) or prev(Outcome) == "Success")
    // count the failures in each session
    | summarize FailureCountBeforeSuccess=sumif(OutcomeCount, Outcome == "Failure"), StartTime=min(TimeGenerated), EndTime=max(TimeGenerated), make_list(Outcome, 128), make_set(Computer, 128), make_set(IpAddress, 128) by SessionStartedUtc, Account
    // the session must not start with a success, and must end with one
    | where array_index_of(list_Outcome, "Success") != 0
    | where array_index_of(list_Outcome, "Success") == array_length(list_Outcome) - 1
    | project-away SessionStartedUtc, list_Outcome
    // where the number of failures before the success is above the threshold
    | where FailureCountBeforeSuccess >= authenticationThreshold
    // expand out ip and computer for customer entity assignment
    | mv-expand set_IpAddress, set_Computer
    | extend IpAddress = tostring(set_IpAddress), Computer = tostring(set_Computer)
    | extend timestamp=StartTime, NTDomain = split(Account, '\\', 0)[0], Name = split(Account, '\\', 1)[0], HostName = tostring(split(Computer, '.', 0)[0]), DnsDomain = tostring(strcat_array(array_slice(split(Computer, '.'), 1, -1), '.'))
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: Account
      - identifier: Name
        columnName: Name
      - identifier: NTDomain
        columnName: NTDomain
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Computer
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: DnsDomain
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: IpAddress
version: 1.0.7
kind: Scheduled