Failed logon attempts in authpriv

let threshold = 15;
// Below pulls messages from syslog-authpriv logs where there was an authentication failure with an unknown user.
// IP address of system attempting logon is also extracted from the SyslogMessage field. Some of these messages
// are aggregated.
Syslog
| where Facility =~ "authpriv"
| where SyslogMessage has "authentication failure" and SyslogMessage has " uid=0"
| extend RemoteIP = extract(@".*?rhost=([\d.]+).*?", 1,SyslogMessage)
| project TimeGenerated, Computer, ProcessName, HostIP, RemoteIP, ProcessID
| join kind=innerunique (
    // Below pulls messages from syslog-authpriv logs that show each instance an unknown user tried to logon. 
    Syslog 
    | where Facility =~ "authpriv"
    | where SyslogMessage has "user unknown"
    | project Computer, HostIP, ProcessID
    ) on Computer, HostIP, ProcessID
// Count the number of failed logon attempts by External IP and internal machine
| summarize FirstLogonAttempt = min(TimeGenerated), LatestLogonAttempt = max(TimeGenerated), TotalLogonAttempts = count() by Computer, HostIP, RemoteIP
// Calculate the time between first and last logon attempt (AttemptPeriodLength)
| extend TimeBetweenLogonAttempts = LatestLogonAttempt - FirstLogonAttempt
| where TotalLogonAttempts >= threshold
| project FirstLogonAttempt, LatestLogonAttempt, TimeBetweenLogonAttempts, TotalLogonAttempts, SourceAddress = RemoteIP, Computer,  HostIP
| sort by Computer asc nulls last

relevantTechniques:
- T1110
name: Failed logon attempts in authpriv
requiredDataConnectors:
- dataTypes:
  - Syslog
  connectorId: Syslog
- dataTypes:
  - Syslog
  connectorId: SyslogAma
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: Computer
  entityType: Host
- fieldMappings:
  - identifier: Address
    columnName: HostIP
  entityType: IP
triggerThreshold: 0
id: e7ec9fa6-e7f7-41ed-a34b-b956837a3ee6
tactics:
- CredentialAccess
version: 1.0.5
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Syslog/Analytic Rules/FailedLogonAttempts_UnknownUser.yaml
queryPeriod: 1d
kind: Scheduled
queryFrequency: 1d
severity: Medium
description: |
  'Identifies failed logon attempts from unknown users in Syslog authpriv logs. The unknown user means the account that tried to log in isn't provisioned on the machine. A few hits could indicate someone attempting to access a machine they aren't authorized to access. 
  If there are many of hits, especially from outside your network, it could indicate a brute force attack. 
  Default threshold for logon attempts is 15.'  
query: |
  let threshold = 15;
  // Below pulls messages from syslog-authpriv logs where there was an authentication failure with an unknown user.
  // IP address of system attempting logon is also extracted from the SyslogMessage field. Some of these messages
  // are aggregated.
  Syslog
  | where Facility =~ "authpriv"
  | where SyslogMessage has "authentication failure" and SyslogMessage has " uid=0"
  | extend RemoteIP = extract(@".*?rhost=([\d.]+).*?", 1,SyslogMessage)
  | project TimeGenerated, Computer, ProcessName, HostIP, RemoteIP, ProcessID
  | join kind=innerunique (
      // Below pulls messages from syslog-authpriv logs that show each instance an unknown user tried to logon. 
      Syslog 
      | where Facility =~ "authpriv"
      | where SyslogMessage has "user unknown"
      | project Computer, HostIP, ProcessID
      ) on Computer, HostIP, ProcessID
  // Count the number of failed logon attempts by External IP and internal machine
  | summarize FirstLogonAttempt = min(TimeGenerated), LatestLogonAttempt = max(TimeGenerated), TotalLogonAttempts = count() by Computer, HostIP, RemoteIP
  // Calculate the time between first and last logon attempt (AttemptPeriodLength)
  | extend TimeBetweenLogonAttempts = LatestLogonAttempt - FirstLogonAttempt
  | where TotalLogonAttempts >= threshold
  | project FirstLogonAttempt, LatestLogonAttempt, TimeBetweenLogonAttempts, TotalLogonAttempts, SourceAddress = RemoteIP, Computer,  HostIP
  | sort by Computer asc nulls last  
triggerOperator: gt

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2024-01-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/e7ec9fa6-e7f7-41ed-a34b-b956837a3ee6')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/e7ec9fa6-e7f7-41ed-a34b-b956837a3ee6')]",
      "properties": {
        "alertRuleTemplateName": "e7ec9fa6-e7f7-41ed-a34b-b956837a3ee6",
        "customDetails": null,
        "description": "'Identifies failed logon attempts from unknown users in Syslog authpriv logs. The unknown user means the account that tried to log in isn't provisioned on the machine. A few hits could indicate someone attempting to access a machine they aren't authorized to access. \nIf there are many of hits, especially from outside your network, it could indicate a brute force attack. \nDefault threshold for logon attempts is 15.'\n",
        "displayName": "Failed logon attempts in authpriv",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "Computer",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "HostIP",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Syslog/Analytic Rules/FailedLogonAttempts_UnknownUser.yaml",
        "query": "let threshold = 15;\n// Below pulls messages from syslog-authpriv logs where there was an authentication failure with an unknown user.\n// IP address of system attempting logon is also extracted from the SyslogMessage field. Some of these messages\n// are aggregated.\nSyslog\n| where Facility =~ \"authpriv\"\n| where SyslogMessage has \"authentication failure\" and SyslogMessage has \" uid=0\"\n| extend RemoteIP = extract(@\".*?rhost=([\\d.]+).*?\", 1,SyslogMessage)\n| project TimeGenerated, Computer, ProcessName, HostIP, RemoteIP, ProcessID\n| join kind=innerunique (\n    // Below pulls messages from syslog-authpriv logs that show each instance an unknown user tried to logon. \n    Syslog \n    | where Facility =~ \"authpriv\"\n    | where SyslogMessage has \"user unknown\"\n    | project Computer, HostIP, ProcessID\n    ) on Computer, HostIP, ProcessID\n// Count the number of failed logon attempts by External IP and internal machine\n| summarize FirstLogonAttempt = min(TimeGenerated), LatestLogonAttempt = max(TimeGenerated), TotalLogonAttempts = count() by Computer, HostIP, RemoteIP\n// Calculate the time between first and last logon attempt (AttemptPeriodLength)\n| extend TimeBetweenLogonAttempts = LatestLogonAttempt - FirstLogonAttempt\n| where TotalLogonAttempts >= threshold\n| project FirstLogonAttempt, LatestLogonAttempt, TimeBetweenLogonAttempts, TotalLogonAttempts, SourceAddress = RemoteIP, Computer,  HostIP\n| sort by Computer asc nulls last\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P1D",
        "severity": "Medium",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CredentialAccess"
        ],
        "techniques": [
          "T1110"
        ],
        "templateVersion": "1.0.5",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}