Detect instances of multiple server errors occurring within a brief period of time (ASIM Web Session)

// HTTP response status codes indicate whether a specific HTTP request has been successfully completed.
// Please refer this for more details: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status
let threshold = 100; // You can update threshold value as per your environment
_Im_WebSession(starttime=ago(1h))
| where toint(EventResultDetails) between (500 .. 599)
| summarize
    TotalErrorCount = count(),
    URLs=make_set(Url, 100),
    EventStartTime = min(TimeGenerated),
    EventEndTime = max(TimeGenerated),
    EventResultDetailsSet=make_set(EventResultDetails,10)
    by SrcIpAddr, bin(TimeGenerated, 5m), SrcUsername, SrcHostname
| where TotalErrorCount > threshold
| extend
    Name = iif(SrcUsername contains "@", tostring(split(SrcUsername, '@', 0)[0]), SrcUsername),
    UPNSuffix = iif(SrcUsername contains "@", tostring(split(SrcUsername, '@', 1)[0]), ""), Threshold=threshold

tags:
- Schema: WebSession
  SchemaVersion: 0.2.6
customDetails:
  RequestURLs: URLs
  TotalErrorCount: TotalErrorCount
  EventResultSet: EventResultDetailsSet
  EventStartTime: EventStartTime
  EventEndTime: EventEndTime
  ErrorThreshold: Threshold
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Web Session Essentials/Analytic Rules/MultipleServerErrorsWithinShortTime.yaml
requiredDataConnectors: []
alertDetailsOverride:
  alertDescriptionFormat: "The client has made a total of '{{TotalErrorCount}}' requests to URLs '{{URLs}}', which have resulted in server errors. It is recommended to thoroughly investigate this alert to determine the underlying cause behind this significant number of errors. For detailed information regarding the specific errors encountered, please refer to the following link: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status."
  alertDisplayNameFormat: High number of server errors originated by user '{{SrcUsername}}' from IP address '{{SrcIpAddr}}'
id: a59ba76c-0205-4966-948e-3d5640140688
tactics:
- InitialAccess
- Impact
queryFrequency: 1h
eventGroupingSettings:
  aggregationKind: AlertPerResult
triggerOperator: gt
relevantTechniques:
- T1190
- T1133
- T1498
description: |
    'This detection mechanism identifies situations where multiple server errors originate from a single source within a limited time frame.'
triggerThreshold: 0
kind: Scheduled
name: Detect instances of multiple server errors occurring within a brief period of time (ASIM Web Session)
query: |
  // HTTP response status codes indicate whether a specific HTTP request has been successfully completed.
  // Please refer this for more details: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status
  let threshold = 100; // You can update threshold value as per your environment
  _Im_WebSession(starttime=ago(1h))
  | where toint(EventResultDetails) between (500 .. 599)
  | summarize
      TotalErrorCount = count(),
      URLs=make_set(Url, 100),
      EventStartTime = min(TimeGenerated),
      EventEndTime = max(TimeGenerated),
      EventResultDetailsSet=make_set(EventResultDetails,10)
      by SrcIpAddr, bin(TimeGenerated, 5m), SrcUsername, SrcHostname
  | where TotalErrorCount > threshold
  | extend
      Name = iif(SrcUsername contains "@", tostring(split(SrcUsername, '@', 0)[0]), SrcUsername),
      UPNSuffix = iif(SrcUsername contains "@", tostring(split(SrcUsername, '@', 1)[0]), ""), Threshold=threshold  
entityMappings:
- entityType: IP
  fieldMappings:
  - columnName: SrcIpAddr
    identifier: Address
- entityType: Account
  fieldMappings:
  - columnName: Name
    identifier: Name
  - columnName: UPNSuffix
    identifier: UPNSuffix
- entityType: Host
  fieldMappings:
  - columnName: SrcHostname
    identifier: HostName
status: Available
severity: Medium
version: 1.0.0
queryPeriod: 1h

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/a59ba76c-0205-4966-948e-3d5640140688')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/a59ba76c-0205-4966-948e-3d5640140688')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "Scheduled",
      "apiVersion": "2022-11-01-preview",
      "properties": {
        "displayName": "Detect instances of multiple server errors occurring within a brief period of time (ASIM Web Session)",
        "description": "'This detection mechanism identifies situations where multiple server errors originate from a single source within a limited time frame.'\n",
        "severity": "Medium",
        "enabled": true,
        "query": "// HTTP response status codes indicate whether a specific HTTP request has been successfully completed.\n// Please refer this for more details: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status\nlet threshold = 100; // You can update threshold value as per your environment\n_Im_WebSession(starttime=ago(1h))\n| where toint(EventResultDetails) between (500 .. 599)\n| summarize\n    TotalErrorCount = count(),\n    URLs=make_set(Url, 100),\n    EventStartTime = min(TimeGenerated),\n    EventEndTime = max(TimeGenerated),\n    EventResultDetailsSet=make_set(EventResultDetails,10)\n    by SrcIpAddr, bin(TimeGenerated, 5m), SrcUsername, SrcHostname\n| where TotalErrorCount > threshold\n| extend\n    Name = iif(SrcUsername contains \"@\", tostring(split(SrcUsername, '@', 0)[0]), SrcUsername),\n    UPNSuffix = iif(SrcUsername contains \"@\", tostring(split(SrcUsername, '@', 1)[0]), \"\"), Threshold=threshold\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0,
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess",
          "Impact"
        ],
        "techniques": [
          "T1190",
          "T1133",
          "T1498"
        ],
        "alertRuleTemplateName": "a59ba76c-0205-4966-948e-3d5640140688",
        "eventGroupingSettings": {
          "aggregationKind": "AlertPerResult"
        },
        "alertDetailsOverride": {
          "alertDisplayNameFormat": "High number of server errors originated by user '{{SrcUsername}}' from IP address '{{SrcIpAddr}}'",
          "alertDescriptionFormat": "The client has made a total of '{{TotalErrorCount}}' requests to URLs '{{URLs}}', which have resulted in server errors. It is recommended to thoroughly investigate this alert to determine the underlying cause behind this significant number of errors. For detailed information regarding the specific errors encountered, please refer to the following link: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status."
        },
        "customDetails": {
          "RequestURLs": "URLs",
          "TotalErrorCount": "TotalErrorCount",
          "EventResultSet": "EventResultDetailsSet",
          "EventStartTime": "EventStartTime",
          "EventEndTime": "EventEndTime",
          "ErrorThreshold": "Threshold"
        },
        "entityMappings": [
          {
            "fieldMappings": [
              {
                "identifier": "Address",
                "columnName": "SrcIpAddr"
              }
            ],
            "entityType": "IP"
          },
          {
            "fieldMappings": [
              {
                "identifier": "Name",
                "columnName": "Name"
              },
              {
                "identifier": "UPNSuffix",
                "columnName": "UPNSuffix"
              }
            ],
            "entityType": "Account"
          },
          {
            "fieldMappings": [
              {
                "identifier": "HostName",
                "columnName": "SrcHostname"
              }
            ],
            "entityType": "Host"
          }
        ],
        "status": "Available",
        "templateVersion": "1.0.0",
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Web Session Essentials/Analytic Rules/MultipleServerErrorsWithinShortTime.yaml",
        "tags": [
          {
            "SchemaVersion": "0.2.6",
            "Schema": "WebSession"
          }
        ]
      }
    }
  ]
}