CTE - Sudden Block Spike Detected | Microsoft Sentinel Analytic Rules

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Id	fbbf3418-f1d8-4bd5-b7da-137a70af6bce
Rulename	CTE - Sudden Block Spike Detected
Description	A sudden spike in blocked URLs/domains on a single device may indicate an active phishing or malware campaign.
Severity	High
Tactics	InitialAccess
Techniques	T1189
Required data connectors	cybereinforce_cte
Kind	Scheduled
Query frequency	10m
Query period	10m
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Cybereinforce/Analytic%20Rules/SuddenBlockSpikeDetected.yaml
Version	1.0.0
Arm template	fbbf3418-f1d8-4bd5-b7da-137a70af6bce.json

KQL

CybereinforceCTE_CL
| where EventType == "block.url"
| extend d = parse_json(Details)
| extend
    DeviceId = tostring(d.deviceId),
    HostName = iff(isnotempty(tostring(d.hostname)), tostring(d.hostname), strcat("cte-device-", substring(EntityId, 0, 8))),
    DeviceUser = tostring(d.deviceUser),
    DeviceOs = tostring(d.deviceOs),
    DeviceVersion = tostring(d.deviceVersion),
    RuleId = tostring(d.ruleId),
    RuleName = iff(isnotempty(tostring(d.ruleName)), tostring(d.ruleName), "Pattern Match"),
    Pattern = tostring(d.pattern),
    Url = tostring(d.url),
    Action = tostring(d.action),
    IsIoc = tobool(d.ioc),
    ClientIp = tostring(split(tostring(d.clientIp), ":")[0]),
    ClientPort = tostring(split(tostring(d.clientIp), ":")[1]),
    UserAgent = tostring(d.userAgent)
| summarize BlockCount=count(), SampleUrls=make_set(Url, 20), SampleIps=make_set(ClientIp, 20), LastHit=max(TimeGenerated) by bin(TimeGenerated, 10m), HostName, DeviceId, DeviceUser, DeviceOs, TenantId
| where BlockCount >= 15
| extend Url = tostring(SampleUrls[0]), ClientIp = tostring(SampleIps[0])

YAML

name: CTE - Sudden Block Spike Detected
triggerOperator: gt
query: |
  CybereinforceCTE_CL
  | where EventType == "block.url"
  | extend d = parse_json(Details)
  | extend
      DeviceId = tostring(d.deviceId),
      HostName = iff(isnotempty(tostring(d.hostname)), tostring(d.hostname), strcat("cte-device-", substring(EntityId, 0, 8))),
      DeviceUser = tostring(d.deviceUser),
      DeviceOs = tostring(d.deviceOs),
      DeviceVersion = tostring(d.deviceVersion),
      RuleId = tostring(d.ruleId),
      RuleName = iff(isnotempty(tostring(d.ruleName)), tostring(d.ruleName), "Pattern Match"),
      Pattern = tostring(d.pattern),
      Url = tostring(d.url),
      Action = tostring(d.action),
      IsIoc = tobool(d.ioc),
      ClientIp = tostring(split(tostring(d.clientIp), ":")[0]),
      ClientPort = tostring(split(tostring(d.clientIp), ":")[1]),
      UserAgent = tostring(d.userAgent)
  | summarize BlockCount=count(), SampleUrls=make_set(Url, 20), SampleIps=make_set(ClientIp, 20), LastHit=max(TimeGenerated) by bin(TimeGenerated, 10m), HostName, DeviceId, DeviceUser, DeviceOs, TenantId
  | where BlockCount >= 15
  | extend Url = tostring(SampleUrls[0]), ClientIp = tostring(SampleIps[0])
queryFrequency: 10m
description: |
  A sudden spike in blocked URLs/domains on a single device may indicate an active phishing or malware campaign.
id: fbbf3418-f1d8-4bd5-b7da-137a70af6bce
triggerThreshold: 0
queryPeriod: 10m
version: 1.0.0
kind: Scheduled
relevantTechniques:
- T1189
severity: High
requiredDataConnectors:
- connectorId: cybereinforce_cte
  dataTypes:
  - CybereinforceCTE_CL
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Cybereinforce/Analytic%20Rules/SuddenBlockSpikeDetected.yaml
tactics:
- InitialAccess
entityMappings:
- fieldMappings:
  - identifier: HostName
    columnName: HostName
  entityType: Host
- fieldMappings:
  - identifier: Url
    columnName: Url
  entityType: URL
- fieldMappings:
  - identifier: Address
    columnName: ClientIp
  entityType: IP

ARM

{
  "$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/fbbf3418-f1d8-4bd5-b7da-137a70af6bce')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/fbbf3418-f1d8-4bd5-b7da-137a70af6bce')]",
      "properties": {
        "alertRuleTemplateName": "fbbf3418-f1d8-4bd5-b7da-137a70af6bce",
        "customDetails": null,
        "description": "A sudden spike in blocked URLs/domains on a single device may indicate an active phishing or malware campaign.\n",
        "displayName": "CTE - Sudden Block Spike Detected",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "HostName",
                "identifier": "HostName"
              }
            ]
          },
          {
            "entityType": "URL",
            "fieldMappings": [
              {
                "columnName": "Url",
                "identifier": "Url"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "ClientIp",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Cybereinforce/Analytic%20Rules/SuddenBlockSpikeDetected.yaml",
        "query": "CybereinforceCTE_CL\n| where EventType == \"block.url\"\n| extend d = parse_json(Details)\n| extend\n    DeviceId = tostring(d.deviceId),\n    HostName = iff(isnotempty(tostring(d.hostname)), tostring(d.hostname), strcat(\"cte-device-\", substring(EntityId, 0, 8))),\n    DeviceUser = tostring(d.deviceUser),\n    DeviceOs = tostring(d.deviceOs),\n    DeviceVersion = tostring(d.deviceVersion),\n    RuleId = tostring(d.ruleId),\n    RuleName = iff(isnotempty(tostring(d.ruleName)), tostring(d.ruleName), \"Pattern Match\"),\n    Pattern = tostring(d.pattern),\n    Url = tostring(d.url),\n    Action = tostring(d.action),\n    IsIoc = tobool(d.ioc),\n    ClientIp = tostring(split(tostring(d.clientIp), \":\")[0]),\n    ClientPort = tostring(split(tostring(d.clientIp), \":\")[1]),\n    UserAgent = tostring(d.userAgent)\n| summarize BlockCount=count(), SampleUrls=make_set(Url, 20), SampleIps=make_set(ClientIp, 20), LastHit=max(TimeGenerated) by bin(TimeGenerated, 10m), HostName, DeviceId, DeviceUser, DeviceOs, TenantId\n| where BlockCount >= 15\n| extend Url = tostring(SampleUrls[0]), ClientIp = tostring(SampleIps[0])\n",
        "queryFrequency": "PT10M",
        "queryPeriod": "PT10M",
        "severity": "High",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess"
        ],
        "techniques": [
          "T1189"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}