NRT Malicious Inbox Rule

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Id	b79f6190-d104-4691-b7db-823e05980895
Rulename	NRT Malicious Inbox Rule
Description	Often times after the initial compromise the attackers create inbox rules to delete emails that contain certain keywords. This is done so as to limit ability to warn compromised users that they’ve been compromised. Below is a sample query that tries to detect this. Reference: https://www.reddit.com/r/sysadmin/comments/7kyp0a/recent_phishing_attempts_my_experience_and_what/
Severity	Medium
Tactics	Persistence DefenseEvasion
Techniques	T1098 T1078
Required data connectors	Office365
Kind	NRT
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Detections/OfficeActivity/NRT_Malicious_Inbox_Rule.yaml
Version	1.0.2
Arm template	b79f6190-d104-4691-b7db-823e05980895.json

KQL

let Keywords = dynamic(["helpdesk", " alert", " suspicious", "fake", "malicious", "phishing", "spam", "do not click", "do not open", "hijacked", "Fatal"]);
OfficeActivity
| where OfficeWorkload =~ "Exchange"
| where Parameters has "Deleted Items" or Parameters has "Junk Email"  or Parameters has "DeleteMessage"
| extend Events=todynamic(Parameters)
| parse Events  with * "SubjectContainsWords" SubjectContainsWords '}'*
| parse Events  with * "BodyContainsWords" BodyContainsWords '}'*
| parse Events  with * "SubjectOrBodyContainsWords" SubjectOrBodyContainsWords '}'*
| where SubjectContainsWords has_any (Keywords)
 or BodyContainsWords has_any (Keywords)
 or SubjectOrBodyContainsWords has_any (Keywords)
| extend ClientIPAddress = case( ClientIP has ".", tostring(split(ClientIP,":")[0]), ClientIP has "[", tostring(trim_start(@'[[]',tostring(split(ClientIP,"]")[0]))), ClientIP )
| extend Keyword = iff(isnotempty(SubjectContainsWords), SubjectContainsWords, (iff(isnotempty(BodyContainsWords),BodyContainsWords,SubjectOrBodyContainsWords )))
| extend RuleDetail = case(OfficeObjectId contains '/' , tostring(split(OfficeObjectId, '/')[-1]) , tostring(split(OfficeObjectId, '\\')[-1]))
| summarize count(), StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated) by  UserId, ClientIPAddress, ResultStatus, Keyword, OriginatingServer, OfficeObjectId, RuleDetail

YAML

description: |
  'Often times after the initial compromise the attackers create inbox rules to delete emails that contain certain keywords.
   This is done so as to limit ability to warn compromised users that they've been compromised. Below is a sample query that tries to detect this.
  Reference: https://www.reddit.com/r/sysadmin/comments/7kyp0a/recent_phishing_attempts_my_experience_and_what/'  
version: 1.0.2
metadata:
  categories:
    domains:
    - Security - Threat Protection
  source:
    kind: Community
  support:
    tier: Community
  author:
    name: Pete Bryan
relevantTechniques:
- T1098
- T1078
kind: NRT
requiredDataConnectors:
- connectorId: Office365
  dataTypes:
  - OfficeActivity
entityMappings:
- fieldMappings:
  - identifier: FullName
    columnName: UserId
  entityType: Account
- fieldMappings:
  - identifier: FullName
    columnName: OriginatingServer
  entityType: Host
- fieldMappings:
  - identifier: Address
    columnName: ClientIPAddress
  entityType: IP
id: b79f6190-d104-4691-b7db-823e05980895
tactics:
- Persistence
- DefenseEvasion
query: |
  let Keywords = dynamic(["helpdesk", " alert", " suspicious", "fake", "malicious", "phishing", "spam", "do not click", "do not open", "hijacked", "Fatal"]);
  OfficeActivity
  | where OfficeWorkload =~ "Exchange"
  | where Parameters has "Deleted Items" or Parameters has "Junk Email"  or Parameters has "DeleteMessage"
  | extend Events=todynamic(Parameters)
  | parse Events  with * "SubjectContainsWords" SubjectContainsWords '}'*
  | parse Events  with * "BodyContainsWords" BodyContainsWords '}'*
  | parse Events  with * "SubjectOrBodyContainsWords" SubjectOrBodyContainsWords '}'*
  | where SubjectContainsWords has_any (Keywords)
   or BodyContainsWords has_any (Keywords)
   or SubjectOrBodyContainsWords has_any (Keywords)
  | extend ClientIPAddress = case( ClientIP has ".", tostring(split(ClientIP,":")[0]), ClientIP has "[", tostring(trim_start(@'[[]',tostring(split(ClientIP,"]")[0]))), ClientIP )
  | extend Keyword = iff(isnotempty(SubjectContainsWords), SubjectContainsWords, (iff(isnotempty(BodyContainsWords),BodyContainsWords,SubjectOrBodyContainsWords )))
  | extend RuleDetail = case(OfficeObjectId contains '/' , tostring(split(OfficeObjectId, '/')[-1]) , tostring(split(OfficeObjectId, '\\')[-1]))
  | summarize count(), StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated) by  UserId, ClientIPAddress, ResultStatus, Keyword, OriginatingServer, OfficeObjectId, RuleDetail  
name: NRT Malicious Inbox Rule
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/OfficeActivity/NRT_Malicious_Inbox_Rule.yaml
severity: Medium

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/b79f6190-d104-4691-b7db-823e05980895')]",
      "kind": "NRT",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/b79f6190-d104-4691-b7db-823e05980895')]",
      "properties": {
        "alertRuleTemplateName": "b79f6190-d104-4691-b7db-823e05980895",
        "customDetails": null,
        "description": "'Often times after the initial compromise the attackers create inbox rules to delete emails that contain certain keywords.\n This is done so as to limit ability to warn compromised users that they've been compromised. Below is a sample query that tries to detect this.\nReference: https://www.reddit.com/r/sysadmin/comments/7kyp0a/recent_phishing_attempts_my_experience_and_what/'\n",
        "displayName": "NRT Malicious Inbox Rule",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "UserId",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "Host",
            "fieldMappings": [
              {
                "columnName": "OriginatingServer",
                "identifier": "FullName"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "ClientIPAddress",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Detections/OfficeActivity/NRT_Malicious_Inbox_Rule.yaml",
        "query": "let Keywords = dynamic([\"helpdesk\", \" alert\", \" suspicious\", \"fake\", \"malicious\", \"phishing\", \"spam\", \"do not click\", \"do not open\", \"hijacked\", \"Fatal\"]);\nOfficeActivity\n| where OfficeWorkload =~ \"Exchange\"\n| where Parameters has \"Deleted Items\" or Parameters has \"Junk Email\"  or Parameters has \"DeleteMessage\"\n| extend Events=todynamic(Parameters)\n| parse Events  with * \"SubjectContainsWords\" SubjectContainsWords '}'*\n| parse Events  with * \"BodyContainsWords\" BodyContainsWords '}'*\n| parse Events  with * \"SubjectOrBodyContainsWords\" SubjectOrBodyContainsWords '}'*\n| where SubjectContainsWords has_any (Keywords)\n or BodyContainsWords has_any (Keywords)\n or SubjectOrBodyContainsWords has_any (Keywords)\n| extend ClientIPAddress = case( ClientIP has \".\", tostring(split(ClientIP,\":\")[0]), ClientIP has \"[\", tostring(trim_start(@'[[]',tostring(split(ClientIP,\"]\")[0]))), ClientIP )\n| extend Keyword = iff(isnotempty(SubjectContainsWords), SubjectContainsWords, (iff(isnotempty(BodyContainsWords),BodyContainsWords,SubjectOrBodyContainsWords )))\n| extend RuleDetail = case(OfficeObjectId contains '/' , tostring(split(OfficeObjectId, '/')[-1]) , tostring(split(OfficeObjectId, '\\\\')[-1]))\n| summarize count(), StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated) by  UserId, ClientIPAddress, ResultStatus, Keyword, OriginatingServer, OfficeObjectId, RuleDetail\n",
        "severity": "Medium",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "DefenseEvasion",
          "Persistence"
        ],
        "techniques": [
          "T1078",
          "T1098"
        ],
        "templateVersion": "1.0.2"
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}