Detect potential file enumeration activity 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 HTTPErrorCode=dynamic(["404"]);
let threshold = 10; // You can update this threshold to the value that suites your environment
// let FileNotFoundRequests = 
_Im_WebSession (starttime=ago(1h))
| where EventResultDetails in~ (HTTPErrorCode)
// Filter the logs to include only HTTP GET requests with an HTTP status code of 404 and '/' in the URL
| where HttpRequestMethod =~ "GET" and Url contains "/"
| summarize
    RequestCount = count(),
    FileCount=dcount(Url),
    EventStartTime=min(TimeGenerated),
    EventEndTime=max(TimeGenerated),
    RequestURLs = make_set(Url, 100),
    DestinationIPList=make_set(DstIpAddr, 100)
    by SrcIpAddr, SrcUsername, SrcHostname, DstHostname
| where RequestCount > threshold  // Adjust the threshold as per your requirements
| extend Name = iif(SrcUsername contains "@", tostring(split(SrcUsername,'@',0)[0]),SrcUsername), UPNSuffix = iif(SrcUsername contains "@",tostring(split(SrcUsername,'@',1)[0]),"")

customDetails:
  RequestCount: RequestCount
  FileCount: FileCount
  RequestURLs: RequestURLs
  EventStartTime: EventStartTime
  EventEndTime: EventEndTime
  DestinationIPList: DestinationIPList
triggerOperator: gt
queryFrequency: 1h
description: |
    'This detection method identifies potential cases of file enumeration activity. The query is designed to identify client sources that generate multiple requests resulting in 404 error codes'
alertDetailsOverride:
  alertDescriptionFormat: User generated multiple requests '{{RequestCount}}' that has resulted in error code '404', suggesting the possibility of file enumeration activity. It's important to investigate the source and patterns of these extensive 404 errors to identify potential security threats. Details about this error code could be found [here](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status)
  alertDisplayNameFormat: User '{{SrcUsername}}' with IP '{{SrcIpAddr}}' has been observed with performing file enumeration activity
status: Available
kind: Scheduled
triggerThreshold: 0
requiredDataConnectors: []
version: 1.0.0
eventGroupingSettings:
  aggregationKind: AlertPerResult
queryPeriod: 1h
name: Detect potential file enumeration activity (ASIM Web Session)
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Web Session Essentials/Analytic Rules/PotentionalFileEnumeration.yaml
id: b3731ce1-1f04-47c4-95c2-9827408c4375
tags:
- Schema: WebSession
  SchemaVersion: 0.2.6
tactics:
- Discovery
- CommandAndControl
- CredentialAccess
relevantTechniques:
- T1083
- T1071
- T1110
severity: Medium
entityMappings:
- fieldMappings:
  - identifier: Address
    columnName: SrcIpAddr
  entityType: IP
- fieldMappings:
  - identifier: Name
    columnName: Name
  - identifier: UPNSuffix
    columnName: UPNSuffix
  entityType: Account
- fieldMappings:
  - identifier: HostName
    columnName: DstHostname
  entityType: Host
- fieldMappings:
  - identifier: HostName
    columnName: SrcHostname
  entityType: Host
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 HTTPErrorCode=dynamic(["404"]);
  let threshold = 10; // You can update this threshold to the value that suites your environment
  // let FileNotFoundRequests = 
  _Im_WebSession (starttime=ago(1h))
  | where EventResultDetails in~ (HTTPErrorCode)
  // Filter the logs to include only HTTP GET requests with an HTTP status code of 404 and '/' in the URL
  | where HttpRequestMethod =~ "GET" and Url contains "/"
  | summarize
      RequestCount = count(),
      FileCount=dcount(Url),
      EventStartTime=min(TimeGenerated),
      EventEndTime=max(TimeGenerated),
      RequestURLs = make_set(Url, 100),
      DestinationIPList=make_set(DstIpAddr, 100)
      by SrcIpAddr, SrcUsername, SrcHostname, DstHostname
  | where RequestCount > threshold  // Adjust the threshold as per your requirements
  | extend Name = iif(SrcUsername contains "@", tostring(split(SrcUsername,'@',0)[0]),SrcUsername), UPNSuffix = iif(SrcUsername contains "@",tostring(split(SrcUsername,'@',1)[0]),"")  

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2023-02-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/b3731ce1-1f04-47c4-95c2-9827408c4375')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/b3731ce1-1f04-47c4-95c2-9827408c4375')]",
      "properties": {
        "alertDetailsOverride": {
          "alertDescriptionFormat": "User generated multiple requests '{{RequestCount}}' that has resulted in error code '404', suggesting the possibility of file enumeration activity. It's important to investigate the source and patterns of these extensive 404 errors to identify potential security threats. Details about this error code could be found [here](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status)",
          "alertDisplayNameFormat": "User '{{SrcUsername}}' with IP '{{SrcIpAddr}}' has been observed with performing file enumeration activity"
        },
        "alertRuleTemplateName": "b3731ce1-1f04-47c4-95c2-9827408c4375",
        "customDetails": {
          "DestinationIPList": "DestinationIPList",
          "EventEndTime": "EventEndTime",
          "EventStartTime": "EventStartTime",
          "FileCount": "FileCount",
          "RequestCount": "RequestCount",
          "RequestURLs": "RequestURLs"
        },
        "description": "'This detection method identifies potential cases of file enumeration activity. The query is designed to identify client sources that generate multiple requests resulting in 404 error codes'\n",
        "displayName": "Detect potential file enumeration activity (ASIM Web Session)",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SrcIpAddr",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "Name",
                "identifier": "Name"
              },
              {
                "columnName": "UPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "DstHostname",
                "identifier": "HostName"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "SrcHostname",
                "identifier": "HostName"
              }
            ]
          }
        ],
        "eventGroupingSettings": {
          "aggregationKind": "AlertPerResult"
        },
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Web Session Essentials/Analytic Rules/PotentionalFileEnumeration.yaml",
        "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 HTTPErrorCode=dynamic([\"404\"]);\nlet threshold = 10; // You can update this threshold to the value that suites your environment\n// let FileNotFoundRequests = \n_Im_WebSession (starttime=ago(1h))\n| where EventResultDetails in~ (HTTPErrorCode)\n// Filter the logs to include only HTTP GET requests with an HTTP status code of 404 and '/' in the URL\n| where HttpRequestMethod =~ \"GET\" and Url contains \"/\"\n| summarize\n    RequestCount = count(),\n    FileCount=dcount(Url),\n    EventStartTime=min(TimeGenerated),\n    EventEndTime=max(TimeGenerated),\n    RequestURLs = make_set(Url, 100),\n    DestinationIPList=make_set(DstIpAddr, 100)\n    by SrcIpAddr, SrcUsername, SrcHostname, DstHostname\n| where RequestCount > threshold  // Adjust the threshold as per your requirements\n| extend Name = iif(SrcUsername contains \"@\", tostring(split(SrcUsername,'@',0)[0]),SrcUsername), UPNSuffix = iif(SrcUsername contains \"@\",tostring(split(SrcUsername,'@',1)[0]),\"\")\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl",
          "CredentialAccess",
          "Discovery"
        ],
        "tags": [
          {
            "Schema": "WebSession",
            "SchemaVersion": "0.2.6"
          }
        ],
        "techniques": [
          "T1071",
          "T1083",
          "T1110"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}