ProofpointPOD - Email sender IP in TI list

Severity: medium
Time window: 14d
Group by: ClientIP, IndicatorId, TI_ipEntity
Source: github.com/Azure/Azure-Sentinel

'Email sender IP in TI list.'

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1078` Valid Accounts
Exfiltration	`T1567` Exfiltration Over Web Service

Rule body

id: 78979d32-e63f-4740-b206-cfb300c735e0
name: ProofpointPOD - Email sender IP in TI list
description: |
  'Email sender IP in TI list.'
severity: Medium
requiredDataConnectors:
  - connectorId: ThreatIntelligence
    dataTypes:
      - ThreatIntelligenceIndicator
  - connectorId: ThreatIntelligenceTaxii
    dataTypes:
      - ThreatIntelligenceIndicator
  - connectorId: ProofpointPOD
    dataTypes:
      - ProofpointPOD_maillog_CL
queryFrequency: 1d
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Exfiltration
  - InitialAccess
relevantTechniques:
  - T1078
  - T1567
query: |
  let dt_lookBack = 1h;
  let ioc_lookBack = 14d;
  ThreatIntelligenceIndicator
  | where TimeGenerated >= ago(ioc_lookBack) and ExpirationDateTime > now()
  | where isnotempty(NetworkIP) or isnotempty(EmailSourceIpAddress) or isnotempty(NetworkDestinationIP) or isnotempty(NetworkSourceIP)
  | extend TI_ipEntity = iff(isnotempty(NetworkIP), NetworkIP, NetworkDestinationIP)
  | extend TI_ipEntity = iff(isempty(TI_ipEntity) and isnotempty(NetworkSourceIP), NetworkSourceIP, TI_ipEntity)
  | extend TI_ipEntity = iff(isempty(TI_ipEntity) and isnotempty(EmailSourceIpAddress), EmailSourceIpAddress, TI_ipEntity)
  | summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId
  | where Active == true
  // using innerunique to keep perf fast and result set low, we only need one match to indicate potential malicious activity that needs to be investigated
  | join kind=innerunique (
            ProofpointPOD 
            | where TimeGenerated >= ago(dt_lookBack)
            | where isnotempty(SrcIpAddr)
            | extend ProofpointPOD_TimeGenerated = TimeGenerated, ClientIP = SrcIpAddr
    )
  on $left.TI_ipEntity == $right.ClientIP
  | where ProofpointPOD_TimeGenerated < ExpirationDateTime
  | summarize ProofpointPOD_TimeGenerated = arg_max(ProofpointPOD_TimeGenerated, *) by IndicatorId, ClientIP
  | project ProofpointPOD_TimeGenerated, SrcUserUpn, DstUserUpn, SrcIpAddr, IndicatorId, ThreatType, ExpirationDateTime, ConfidenceScore,
  TI_ipEntity, ClientIP
  | extend timestamp = ProofpointPOD_TimeGenerated
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: SrcUserUpn
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: ClientIP
version: 1.1.1
kind: Scheduled

Stages and Predicates

Parameters

let dt_lookBack = 1h;
let ioc_lookBack = 14d;

Stage 1: `source`

ThreatIntelligenceIndicator

Stage 2: `where`

| where TimeGenerated >= ago(ioc_lookBack) and ExpirationDateTime > now()

Stage 3: `where`

| where isnotempty(NetworkIP) or isnotempty(EmailSourceIpAddress) or isnotempty(NetworkDestinationIP) or isnotempty(NetworkSourceIP)

Stage 4: `extend` (3 consecutive steps)

| extend TI_ipEntity = iff(isnotempty(NetworkIP), NetworkIP, NetworkDestinationIP)
| extend TI_ipEntity = iff(isempty(TI_ipEntity) and isnotempty(NetworkSourceIP), NetworkSourceIP, TI_ipEntity)
| extend TI_ipEntity = iff(isempty(TI_ipEntity) and isnotempty(EmailSourceIpAddress), EmailSourceIpAddress, TI_ipEntity)

TI_ipEntity =

ifisnotempty(NetworkIP)NetworkIP

elseNetworkDestinationIP

Stage 5: `summarize`

| summarize LatestIndicatorTime = arg_max(TimeGenerated, *) by IndicatorId

Stage 6: `where`

| where Active == true

Stage 7: `join`

| join kind=innerunique (
          ProofpointPOD 
          | where TimeGenerated >= ago(dt_lookBack)
          | where isnotempty(SrcIpAddr)
          | extend ProofpointPOD_TimeGenerated = TimeGenerated, ClientIP = SrcIpAddr
  )
on $left.TI_ipEntity == $right.ClientIP

Stage 8: `where`

| where ProofpointPOD_TimeGenerated < ExpirationDateTime

Stage 9: `summarize`

| summarize ProofpointPOD_TimeGenerated = arg_max(ProofpointPOD_TimeGenerated, *) by IndicatorId, ClientIP

Stage 10: `project`

| project ProofpointPOD_TimeGenerated, SrcUserUpn, DstUserUpn, SrcIpAddr, IndicatorId, ThreatType, ExpirationDateTime, ConfidenceScore,
TI_ipEntity, ClientIP

Stage 11: `extend`

| extend timestamp = ProofpointPOD_TimeGenerated

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Active`	eq	`true`	`field:"Active" kind:eq value:"true"`
`EmailSourceIpAddress`	is_not_null	(no value, null check)	`field:"EmailSourceIpAddress" kind:is_not_null`
`NetworkDestinationIP`	is_not_null	(no value, null check)	`field:"NetworkDestinationIP" kind:is_not_null`
`NetworkIP`	is_not_null	(no value, null check)	`field:"NetworkIP" kind:is_not_null`
`NetworkSourceIP`	is_not_null	(no value, null check)	`field:"NetworkSourceIP" kind:is_not_null`
`ProofpointPOD_TimeGenerated`	cross_field_compare	`ExpirationDateTime` transforms: `op:lt`	`field:"ProofpointPOD_TimeGenerated" kind:cross_field_compare value:"ExpirationDateTime"`
`SrcIpAddr`	is_not_null	(no value, null check)	`field:"src_ip" kind:is_not_null`

Output fields

These fields are emitted when the rule matches.

Field	Source
`ClientIP`	`project`
`ConfidenceScore`	`project`
`DstUserUpn`	`project`
`ExpirationDateTime`	`project`
`IndicatorId`	`project`
`ProofpointPOD_TimeGenerated`	`project`
`SrcIpAddr`	`project`
`SrcUserUpn`	`project`
`TI_ipEntity`	`project`
`ThreatType`	`project`
`timestamp`	`extend`

ProofpointPOD - Email sender IP in TI list

MITRE ATT&CK coverage

Rule body

Stages and Predicates

Parameters

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: extend (3 consecutive steps)

Stage 5: summarize

Stage 6: where

Stage 7: join

Stage 8: where

Stage 9: summarize

Stage 10: project

Stage 11: extend