Microsoft Sentinel Analytic Rules
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Egress Defend - Dangerous Attachment Detected

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Ida0e55dd4-8454-4396-91e6-f28fec3d2cab
RulenameEgress Defend - Dangerous Attachment Detected
DescriptionDefend has detected a user has a suspicious file type from a suspicious sender in their mailbox.
SeverityMedium
TacticsExecution
InitialAccess
Persistence
PrivilegeEscalation
TechniquesT1204
T0853
T0863
T1566
T1546
T1546
Required data connectorsEgressDefend
KindScheduled
Query frequency30m
Query period30m
Trigger threshold0
Trigger operatorgt
Source Urihttps://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Egress Defend/Analytic Rules/DangerousAttachmentReceived.yaml
Version1.0.0
Arm templatea0e55dd4-8454-4396-91e6-f28fec3d2cab.json
Deploy To Azure
DefendAuditData
| where ThreatLevel == "suspicious" or ThreatLevel == "dangerous"
| mv-expand todynamic(Attachments)
| where Attachments.name matches regex @"(?i)^.*\.(doc|docx|docm|pdf|xls|xlsx|xlsm|html|zip)$(?-i)"
| summarize attachmentCount=count() by TimeGenerated, tostring(Attachments.name), Subject, From, Account_0_FullName = trim(@"[^@.\w]+",Recipients), timesClicked = LinksClicked, SenderIP
severity: Medium
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Egress Defend/Analytic Rules/DangerousAttachmentReceived.yaml
entityMappings:
- fieldMappings:
  - columnName: Account_0_FullName
    identifier: FullName
  entityType: Account
- fieldMappings:
  - columnName: Attachments_name
    identifier: Name
  entityType: File
- fieldMappings:
  - columnName: Account_0_FullName
    identifier: MailboxPrimaryAddress
  entityType: Mailbox
- fieldMappings:
  - columnName: SenderIP
    identifier: Address
  entityType: IP
id: a0e55dd4-8454-4396-91e6-f28fec3d2cab
name: Egress Defend - Dangerous Attachment Detected
query: |
  DefendAuditData
  | where ThreatLevel == "suspicious" or ThreatLevel == "dangerous"
  | mv-expand todynamic(Attachments)
  | where Attachments.name matches regex @"(?i)^.*\.(doc|docx|docm|pdf|xls|xlsx|xlsm|html|zip)$(?-i)"
  | summarize attachmentCount=count() by TimeGenerated, tostring(Attachments.name), Subject, From, Account_0_FullName = trim(@"[^@.\w]+",Recipients), timesClicked = LinksClicked, SenderIP  
tags:
- Defend
queryPeriod: 30m
triggerThreshold: 0
tactics:
- Execution
- InitialAccess
- Persistence
- PrivilegeEscalation
version: 1.0.0
kind: Scheduled
relevantTechniques:
- T1204
- T0853
- T0863
- T1566
- T1546
- T1546
queryFrequency: 30m
status: Available
requiredDataConnectors:
- dataTypes:
  - EgressDefend_CL
  connectorId: EgressDefend
description: |
    'Defend has detected a user has a suspicious file type from a suspicious sender in their mailbox.'
alertDetailsOverride:
  alertDisplayNameFormat: Alert - {{Account_0_FullName}} has suspicious attachment.
triggerOperator: gt
{
  "$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/a0e55dd4-8454-4396-91e6-f28fec3d2cab')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/a0e55dd4-8454-4396-91e6-f28fec3d2cab')]",
      "properties": {
        "alertDetailsOverride": {
          "alertDisplayNameFormat": "Alert - {{Account_0_FullName}} has suspicious attachment."
        },
        "alertRuleTemplateName": "a0e55dd4-8454-4396-91e6-f28fec3d2cab",
        "customDetails": null,
        "description": "'Defend has detected a user has a suspicious file type from a suspicious sender in their mailbox.'\n",
        "displayName": "Egress Defend - Dangerous Attachment Detected",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "Account_0_FullName",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "File",
            "fieldMappings": [
              {
                "columnName": "Attachments_name",
                "identifier": "Name"
              }
            ]
          },
          {
            "entityType": "Mailbox",
            "fieldMappings": [
              {
                "columnName": "Account_0_FullName",
                "identifier": "MailboxPrimaryAddress"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SenderIP",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Egress Defend/Analytic Rules/DangerousAttachmentReceived.yaml",
        "query": "DefendAuditData\n| where ThreatLevel == \"suspicious\" or ThreatLevel == \"dangerous\"\n| mv-expand todynamic(Attachments)\n| where Attachments.name matches regex @\"(?i)^.*\\.(doc|docx|docm|pdf|xls|xlsx|xlsm|html|zip)$(?-i)\"\n| summarize attachmentCount=count() by TimeGenerated, tostring(Attachments.name), Subject, From, Account_0_FullName = trim(@\"[^@.\\w]+\",Recipients), timesClicked = LinksClicked, SenderIP\n",
        "queryFrequency": "PT30M",
        "queryPeriod": "PT30M",
        "severity": "Medium",
        "status": "Available",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Execution",
          "InitialAccess",
          "Persistence",
          "PrivilegeEscalation"
        ],
        "tags": [
          "Defend"
        ],
        "techniques": [
          "T1204",
          "T1546",
          "T1566"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}