Identify instances where a single source is observed using multiple user agents ASIM Web Session

let threshold = 5; // Please update threshold limit as per your environment
_Im_WebSession(starttime=ago(1h), eventresult="Success")
| where isnotempty(HttpUserAgent)
| summarize
    EventCount=count(),
    UserAgentList=make_set(HttpUserAgent, 100),
    URL_List = make_set(Url, 100),
    DestinationIPList = make_set(DstIpAddr, 100)
    by SrcIpAddr, SrcUsername, SrcHostname, bin(TimeGenerated, 5min)
| extend UserAgentCount = array_length(UserAgentList)
| where UserAgentCount > threshold
| extend Name = iif(SrcUsername contains "@", tostring(split(SrcUsername,'@',0)[0]),SrcUsername), UPNSuffix = iif(SrcUsername contains "@",tostring(split(SrcUsername,'@',1)[0]),""), Threshold=threshold

status: Available
requiredDataConnectors: []
customDetails:
  UserAgentThreshold: Threshold
  DestinationIPList: DestinationIPList
  URLs: URL_List
  UserAgentArray: UserAgentList
  UserAgentCount: UserAgentCount
description: |
  'This detection mechanism identifies requests originating from a single source within a brief time period that exhibit multiple user agents. Such behavior could indicate unusual web browsing activities performed by unconventional processes'
queryPeriod: 1h
version: 1.0.1
name: Identify instances where a single source is observed using multiple user agents (ASIM Web Session)
eventGroupingSettings:
  aggregationKind: AlertPerResult
tags:
- Schema: WebSession
  SchemaVersion: 0.2.6
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Web%20Session%20Essentials/Analytic%20Rules/MultipleUAsFromSingleIP.yaml
alertDetailsOverride:
  alertDescriptionFormat: "The system has detected high User Agent count of '{{UserAgentCount}}' originating from '{{SrcUsername}}'. Further investigation is necessary to determine the reason behind the detection of multiple user agents associated with the SrcIpAddr in this incident. User Agent list include: '{{UserAgentList}}'"
  alertDisplayNameFormat: User '{{SrcUsername}}' with IP '{{SrcIpAddr}}' has been observed using high number of User Agents within short timeframe
entityMappings:
- entityType: IP
  fieldMappings:
  - identifier: Address
    columnName: SrcIpAddr
- entityType: Host
  fieldMappings:
  - identifier: HostName
    columnName: SrcHostname
- entityType: Account
  fieldMappings:
  - identifier: Name
    columnName: Name
  - identifier: UPNSuffix
    columnName: UPNSuffix
relevantTechniques:
- T1190
- T1133
- T1528
query: |
  let threshold = 5; // Please update threshold limit as per your environment
  _Im_WebSession(starttime=ago(1h), eventresult="Success")
  | where isnotempty(HttpUserAgent)
  | summarize
      EventCount=count(),
      UserAgentList=make_set(HttpUserAgent, 100),
      URL_List = make_set(Url, 100),
      DestinationIPList = make_set(DstIpAddr, 100)
      by SrcIpAddr, SrcUsername, SrcHostname, bin(TimeGenerated, 5min)
  | extend UserAgentCount = array_length(UserAgentList)
  | where UserAgentCount > threshold
  | extend Name = iif(SrcUsername contains "@", tostring(split(SrcUsername,'@',0)[0]),SrcUsername), UPNSuffix = iif(SrcUsername contains "@",tostring(split(SrcUsername,'@',1)[0]),""), Threshold=threshold
kind: Scheduled
id: 813ccf3b-0321-4622-b0bc-63518fd14454
triggerOperator: gt
queryFrequency: 1h
tactics:
- InitialAccess
- CredentialAccess
severity: Medium
triggerThreshold: 0

{
  "$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/813ccf3b-0321-4622-b0bc-63518fd14454')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/813ccf3b-0321-4622-b0bc-63518fd14454')]",
      "properties": {
        "alertDetailsOverride": {
          "alertDescriptionFormat": "The system has detected high User Agent count of '{{UserAgentCount}}' originating from '{{SrcUsername}}'. Further investigation is necessary to determine the reason behind the detection of multiple user agents associated with the SrcIpAddr in this incident. User Agent list include: '{{UserAgentList}}'",
          "alertDisplayNameFormat": "User '{{SrcUsername}}' with IP '{{SrcIpAddr}}' has been observed using high number of User Agents within short timeframe"
        },
        "alertRuleTemplateName": "813ccf3b-0321-4622-b0bc-63518fd14454",
        "customDetails": {
          "DestinationIPList": "DestinationIPList",
          "URLs": "URL_List",
          "UserAgentArray": "UserAgentList",
          "UserAgentCount": "UserAgentCount",
          "UserAgentThreshold": "Threshold"
        },
        "description": "'This detection mechanism identifies requests originating from a single source within a brief time period that exhibit multiple user agents. Such behavior could indicate unusual web browsing activities performed by unconventional processes'\n",
        "displayName": "Identify instances where a single source is observed using multiple user agents (ASIM Web Session)",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SrcIpAddr",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "SrcHostname",
                "identifier": "HostName"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "Name",
                "identifier": "Name"
              },
              {
                "columnName": "UPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          }
        ],
        "eventGroupingSettings": {
          "aggregationKind": "AlertPerResult"
        },
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Web%20Session%20Essentials/Analytic%20Rules/MultipleUAsFromSingleIP.yaml",
        "query": "let threshold = 5; // Please update threshold limit as per your environment\n_Im_WebSession(starttime=ago(1h), eventresult=\"Success\")\n| where isnotempty(HttpUserAgent)\n| summarize\n    EventCount=count(),\n    UserAgentList=make_set(HttpUserAgent, 100),\n    URL_List = make_set(Url, 100),\n    DestinationIPList = make_set(DstIpAddr, 100)\n    by SrcIpAddr, SrcUsername, SrcHostname, bin(TimeGenerated, 5min)\n| extend UserAgentCount = array_length(UserAgentList)\n| where UserAgentCount > threshold\n| extend Name = iif(SrcUsername contains \"@\", tostring(split(SrcUsername,'@',0)[0]),SrcUsername), UPNSuffix = iif(SrcUsername contains \"@\",tostring(split(SrcUsername,'@',1)[0]),\"\"), Threshold=threshold\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CredentialAccess",
          "InitialAccess"
        ],
        "tags": [
          {
            "Schema": "WebSession",
            "SchemaVersion": "0.2.6"
          }
        ],
        "techniques": [
          "T1133",
          "T1190",
          "T1528"
        ],
        "templateVersion": "1.0.1",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}