Brute force attack against a Cloud PC

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Id	3fbc20a4-04c4-464e-8fcb-6667f53e4987
Rulename	Brute force attack against a Cloud PC
Description	Identifies evidence of brute force activity against a Windows 365 Cloud PC by highlighting multiple authentication failures and by a successful authentication within a given time window.
Severity	Medium
Tactics	CredentialAccess
Techniques	T1110
Required data connectors	AzureActiveDirectory
Kind	Scheduled
Query frequency	1d
Query period	1d
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Entra ID/Analytic Rules/BruteForceCloudPC.yaml
Version	2.0.1
Arm template	3fbc20a4-04c4-464e-8fcb-6667f53e4987.json

KQL

let authenticationWindow = 20m;
let sensitivity = 2.5;
SigninLogs
| where AppDisplayName =~ "Windows Sign In"
| extend FailureOrSuccess = iff(ResultType in ("0", "50125", "50140", "70043", "70044"), "Success", "Failure")
| summarize FailureCount = countif(FailureOrSuccess=="Failure"), SuccessCount = countif(FailureOrSuccess=="Success"), IPAddresses = make_set(IPAddress,1000)
                          by bin(TimeGenerated, authenticationWindow), UserDisplayName, UserPrincipalName
| extend FailureSuccessDiff = FailureCount - SuccessCount
| where FailureSuccessDiff > 0
| summarize Diff = make_list(FailureSuccessDiff, 10000), TimeStamp = make_list(TimeGenerated, 10000) by UserDisplayName, UserPrincipalName//, tostring(IPAddresses)
| extend (Anomalies, Score, Baseline) = series_decompose_anomalies(Diff, sensitivity, -1, 'linefit')  
| mv-expand Diff to typeof(double), TimeStamp to typeof(datetime), Anomalies to typeof(double), Score to typeof(double), Baseline to typeof(long)
| where Anomalies > 0
| summarize by UserDisplayName, UserPrincipalName, Anomalies, Score, Baseline, FailureToSuccessDiff = Diff
| join kind=leftouter (
      SigninLogs
      | where AppDisplayName =~ "Windows Sign In"
      | extend OS = DeviceDetail.operatingSystem, Browser = DeviceDetail.browser
      | extend StatusCode = tostring(Status.errorCode), StatusDetails = tostring(Status.additionalDetails)
      | extend State = tostring(LocationDetails.state), City = tostring(LocationDetails.city)
      | summarize StartTime = min(TimeGenerated), 
                  EndTime = max(TimeGenerated), 
                  IPAddresses = make_set(IPAddress,100), 
                  OS = make_set(OS,20), 
                  Browser = make_set(Browser,20), 
                  City = make_set(City,100), 
                  ResultType = make_set(ResultType,100)
              by UserDisplayName, UserPrincipalName, UserId, AppDisplayName
  ) on UserDisplayName, UserPrincipalName
| project-away UserDisplayName1, UserPrincipalName1
| extend IPAddressFirst = tostring(IPAddresses[0])
| extend Name = tostring(split(UserPrincipalName,'@',0)[0]), UPNSuffix = tostring(split(UserPrincipalName,'@',1)[0])

YAML

description: |
    'Identifies evidence of brute force activity against a Windows 365 Cloud PC by highlighting multiple authentication failures and by a successful authentication within a given time window.'
kind: Scheduled
tactics:
- CredentialAccess
requiredDataConnectors:
- connectorId: AzureActiveDirectory
  dataTypes:
  - SigninLogs
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Microsoft Entra ID/Analytic Rules/BruteForceCloudPC.yaml
severity: Medium
name: Brute force attack against a Cloud PC
triggerThreshold: 0
queryPeriod: 1d
query: |
  let authenticationWindow = 20m;
  let sensitivity = 2.5;
  SigninLogs
  | where AppDisplayName =~ "Windows Sign In"
  | extend FailureOrSuccess = iff(ResultType in ("0", "50125", "50140", "70043", "70044"), "Success", "Failure")
  | summarize FailureCount = countif(FailureOrSuccess=="Failure"), SuccessCount = countif(FailureOrSuccess=="Success"), IPAddresses = make_set(IPAddress,1000)
                            by bin(TimeGenerated, authenticationWindow), UserDisplayName, UserPrincipalName
  | extend FailureSuccessDiff = FailureCount - SuccessCount
  | where FailureSuccessDiff > 0
  | summarize Diff = make_list(FailureSuccessDiff, 10000), TimeStamp = make_list(TimeGenerated, 10000) by UserDisplayName, UserPrincipalName//, tostring(IPAddresses)
  | extend (Anomalies, Score, Baseline) = series_decompose_anomalies(Diff, sensitivity, -1, 'linefit')  
  | mv-expand Diff to typeof(double), TimeStamp to typeof(datetime), Anomalies to typeof(double), Score to typeof(double), Baseline to typeof(long)
  | where Anomalies > 0
  | summarize by UserDisplayName, UserPrincipalName, Anomalies, Score, Baseline, FailureToSuccessDiff = Diff
  | join kind=leftouter (
        SigninLogs
        | where AppDisplayName =~ "Windows Sign In"
        | extend OS = DeviceDetail.operatingSystem, Browser = DeviceDetail.browser
        | extend StatusCode = tostring(Status.errorCode), StatusDetails = tostring(Status.additionalDetails)
        | extend State = tostring(LocationDetails.state), City = tostring(LocationDetails.city)
        | summarize StartTime = min(TimeGenerated), 
                    EndTime = max(TimeGenerated), 
                    IPAddresses = make_set(IPAddress,100), 
                    OS = make_set(OS,20), 
                    Browser = make_set(Browser,20), 
                    City = make_set(City,100), 
                    ResultType = make_set(ResultType,100)
                by UserDisplayName, UserPrincipalName, UserId, AppDisplayName
    ) on UserDisplayName, UserPrincipalName
  | project-away UserDisplayName1, UserPrincipalName1
  | extend IPAddressFirst = tostring(IPAddresses[0])
  | extend Name = tostring(split(UserPrincipalName,'@',0)[0]), UPNSuffix = tostring(split(UserPrincipalName,'@',1)[0])  
relevantTechniques:
- T1110
id: 3fbc20a4-04c4-464e-8fcb-6667f53e4987
queryFrequency: 1d
status: Available
triggerOperator: gt
version: 2.0.1
entityMappings:
- entityType: Account
  fieldMappings:
  - columnName: UserPrincipalName
    identifier: FullName
  - columnName: Name
    identifier: Name
  - columnName: UPNSuffix
    identifier: UPNSuffix
- entityType: Account
  fieldMappings:
  - columnName: UserId
    identifier: AadUserId
- entityType: IP
  fieldMappings:
  - columnName: IPAddressFirst
    identifier: Address

ARM