NRT Malicious Inbox Rule
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 |
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
version: 1.0.2
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/'
kind: NRT
requiredDataConnectors:
- connectorId: Office365
dataTypes:
- OfficeActivity
name: NRT Malicious Inbox Rule
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Detections/OfficeActivity/NRT_Malicious_Inbox_Rule.yaml
id: b79f6190-d104-4691-b7db-823e05980895
tactics:
- Persistence
- DefenseEvasion
metadata:
source:
kind: Community
author:
name: Pete Bryan
categories:
domains:
- Security - Threat Protection
support:
tier: Community
relevantTechniques:
- T1098
- T1078
severity: Medium
entityMappings:
- fieldMappings:
- identifier: FullName
columnName: UserId
entityType: Account
- fieldMappings:
- identifier: FullName
columnName: OriginatingServer
entityType: Host
- fieldMappings:
- identifier: Address
columnName: ClientIPAddress
entityType: IP
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
{
"$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/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",
"suppressionDuration": "PT1H",
"suppressionEnabled": false,
"tactics": [
"DefenseEvasion",
"Persistence"
],
"techniques": [
"T1078",
"T1098"
],
"templateVersion": "1.0.2"
},
"type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
}
]
}