Microsoft Sentinel Analytic Rules
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Cisco Umbrella - Rare User Agent Detected

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Id8c8de3fa-6425-4623-9cd9-45de1dd0569a
RulenameCisco Umbrella - Rare User Agent Detected
DescriptionRule helps to detect a rare user-agents indicating web browsing activity by an unusual process other than a web browser.
SeverityMedium
TacticsCommandAndControl
Required data connectorsCiscoUmbrellaDataConnector
KindScheduled
Query frequency1d
Query period14d
Trigger threshold0
Trigger operatorgt
Source Urihttps://github.com/Azure/Azure-Sentinel/blob/master/Detections/CiscoUmbrella/CiscoUmbrellaRareUserAgentDetected.yaml
Version1.1.2
Arm template8c8de3fa-6425-4623-9cd9-45de1dd0569a.json
Deploy To Azure
let lookBack = 14d;
let timeframe = 1d;
let user_agents_list = Cisco_Umbrella
| where EventType == "proxylogs"
| where TimeGenerated > ago(lookBack) and TimeGenerated < ago(timeframe)
| summarize count() by HttpUserAgentOriginal
| summarize make_list(HttpUserAgentOriginal);
Cisco_Umbrella
| where EventType == "proxylogs"
| where TimeGenerated > ago(timeframe)
| where HttpUserAgentOriginal !in (user_agents_list)
| extend Message = "Rare User Agent"
| project Message, SrcIpAddr, DstIpAddr, UrlOriginal, TimeGenerated, HttpUserAgentOriginal
name: Cisco Umbrella - Rare User Agent Detected
triggerOperator: gt
query: |
  let lookBack = 14d;
  let timeframe = 1d;
  let user_agents_list = Cisco_Umbrella
  | where EventType == "proxylogs"
  | where TimeGenerated > ago(lookBack) and TimeGenerated < ago(timeframe)
  | summarize count() by HttpUserAgentOriginal
  | summarize make_list(HttpUserAgentOriginal);
  Cisco_Umbrella
  | where EventType == "proxylogs"
  | where TimeGenerated > ago(timeframe)
  | where HttpUserAgentOriginal !in (user_agents_list)
  | extend Message = "Rare User Agent"
  | project Message, SrcIpAddr, DstIpAddr, UrlOriginal, TimeGenerated, HttpUserAgentOriginal  
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/CiscoUmbrella/CiscoUmbrellaRareUserAgentDetected.yaml
description: |
    'Rule helps to detect a rare user-agents indicating web browsing activity by an unusual process other than a web browser.'
triggerThreshold: 0
id: 8c8de3fa-6425-4623-9cd9-45de1dd0569a
kind: Scheduled
severity: Medium
version: 1.1.2
entityMappings:
- fieldMappings:
  - identifier: Url
    columnName: UrlOriginal
  entityType: URL
- fieldMappings:
  - identifier: Address
    columnName: SrcIpAddr
  entityType: IP
queryFrequency: 1d
queryPeriod: 14d
requiredDataConnectors:
- dataTypes:
  - Cisco_Umbrella_proxy_CL
  connectorId: CiscoUmbrellaDataConnector
tactics:
- CommandAndControl
{
  "$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/8c8de3fa-6425-4623-9cd9-45de1dd0569a')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/8c8de3fa-6425-4623-9cd9-45de1dd0569a')]",
      "properties": {
        "alertRuleTemplateName": "8c8de3fa-6425-4623-9cd9-45de1dd0569a",
        "customDetails": null,
        "description": "'Rule helps to detect a rare user-agents indicating web browsing activity by an unusual process other than a web browser.'\n",
        "displayName": "Cisco Umbrella - Rare User Agent Detected",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "URL",
            "fieldMappings": [
              {
                "columnName": "UrlOriginal",
                "identifier": "Url"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SrcIpAddr",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/CiscoUmbrella/CiscoUmbrellaRareUserAgentDetected.yaml",
        "query": "let lookBack = 14d;\nlet timeframe = 1d;\nlet user_agents_list = Cisco_Umbrella\n| where EventType == \"proxylogs\"\n| where TimeGenerated > ago(lookBack) and TimeGenerated < ago(timeframe)\n| summarize count() by HttpUserAgentOriginal\n| summarize make_list(HttpUserAgentOriginal);\nCisco_Umbrella\n| where EventType == \"proxylogs\"\n| where TimeGenerated > ago(timeframe)\n| where HttpUserAgentOriginal !in (user_agents_list)\n| extend Message = \"Rare User Agent\"\n| project Message, SrcIpAddr, DstIpAddr, UrlOriginal, TimeGenerated, HttpUserAgentOriginal\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P14D",
        "severity": "Medium",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl"
        ],
        "templateVersion": "1.1.2",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}