VMware SD-WAN Edge - Network Anomaly Detection - RPF Check Failure

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Id	840b050f-842b-4264-8973-d4f9b65facb5
Rulename	VMware SD-WAN Edge - Network Anomaly Detection - RPF Check Failure
Description	The VMware SD-WAN Edge appliance received packets that failed a Reverse Path Forwarding (RPF) Check. Reverse path forwarding (RPF) check is a network security mechanism that verifies whether the source IP address of a packet is reachable through the incoming interface on which the packet is received. The packet is dropped if the source IP address is not reachable through the incoming interface. RPF checks prevent spoofing attacks, in which an attacker uses a forged source IP address to make it appear that the packets are coming from a trusted source. This can allow the attacker to gain unauthorized network access or launch a denial-of-service attack against a target system. An IP fragmentation attack is a cyberattack that exploits how IP packets are fragmented and reassembled. IP fragmentation is a process by which large IP packets are broken down into smaller packets to transmit them over networks with smaller Maximum Transmission Unit (MTU) sizes. This analytics rule analyzes Syslog streams; these alerts are not reported by default if Search API is used.
Severity	Low
Tactics	Impact
Techniques	T1498
Required data connectors	VMwareSDWAN
Kind	Scheduled
Query frequency	1h
Query period	1h
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/VMware SD-WAN and SASE/Analytic Rules/vmw-sdwan-rpfcheck.yaml
Version	1.0.0
Arm template	840b050f-842b-4264-8973-d4f9b65facb5.json

KQL

Syslog
| where SyslogMessage contains "VCF Drop"
| where SyslogMessage contains "Reverse path forwarding check fail"
| project-rename EdgeName=HostName
| project-away Computer, HostIP, SourceSystem, Type
| extend OverlaySegmentName = extract("SEGMENT_NAME=(.+) COUNT=", 1, SyslogMessage)
| extend IpProtocol = extract("PROTO=(.+) SRC=", 1, SyslogMessage)
| extend SrcIpAddress = extract("SRC=(.+) DST=", 1, SyslogMessage)
| extend DstIpAddress = extract("DST=(.+) REASON=", 1, SyslogMessage)
| extend EdgeFwAction = extract("ACTION=(.+) SEGMENT=", 1, SyslogMessage)
| extend SyslogTag = extract("^(.+): ACTION=", 1, SyslogMessage)
| extend pcktCount = extract("COUNT=([0-9]+)$", 1, SyslogMessage)
| project
    TimeGenerated,
    EdgeFwAction,
    EdgeName,
    SrcIpAddress,
    IpProtocol,
    DstIpAddress,
    pcktCount,
    SyslogTag

YAML

OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/VMware SD-WAN and SASE/Analytic Rules/vmw-sdwan-rpfcheck.yaml
severity: Low
queryFrequency: 1h
version: 1.0.0
suppressionEnabled: false
triggerOperator: gt
query: |+
  Syslog
  | where SyslogMessage contains "VCF Drop"
  | where SyslogMessage contains "Reverse path forwarding check fail"
  | project-rename EdgeName=HostName
  | project-away Computer, HostIP, SourceSystem, Type
  | extend OverlaySegmentName = extract("SEGMENT_NAME=(.+) COUNT=", 1, SyslogMessage)
  | extend IpProtocol = extract("PROTO=(.+) SRC=", 1, SyslogMessage)
  | extend SrcIpAddress = extract("SRC=(.+) DST=", 1, SyslogMessage)
  | extend DstIpAddress = extract("DST=(.+) REASON=", 1, SyslogMessage)
  | extend EdgeFwAction = extract("ACTION=(.+) SEGMENT=", 1, SyslogMessage)
  | extend SyslogTag = extract("^(.+): ACTION=", 1, SyslogMessage)
  | extend pcktCount = extract("COUNT=([0-9]+)$", 1, SyslogMessage)
  | project
      TimeGenerated,
      EdgeFwAction,
      EdgeName,
      SrcIpAddress,
      IpProtocol,
      DstIpAddress,
      pcktCount,
      SyslogTag  

suppressionDuration: 5h
kind: Scheduled
id: 840b050f-842b-4264-8973-d4f9b65facb5
name: VMware SD-WAN Edge - Network Anomaly Detection - RPF Check Failure
requiredDataConnectors:
- dataTypes:
  - SDWAN
  connectorId: VMwareSDWAN
description: |-
  The VMware SD-WAN Edge appliance received packets that failed a Reverse Path Forwarding (RPF) Check.

  Reverse path forwarding (RPF) check is a network security mechanism that verifies whether the source IP address of a packet is reachable through the incoming interface on which the packet is received. The packet is dropped if the source IP address is not reachable through the incoming interface.

  RPF checks prevent spoofing attacks, in which an attacker uses a forged source IP address to make it appear that the packets are coming from a trusted source. This can allow the attacker to gain unauthorized network access or launch a denial-of-service attack against a target system.

  An IP fragmentation attack is a cyberattack that exploits how IP packets are fragmented and reassembled. IP fragmentation is a process by which large IP packets are broken down into smaller packets to transmit them over networks with smaller Maximum Transmission Unit (MTU) sizes.

  This analytics rule analyzes Syslog streams; these alerts are not reported by default if Search API is used.  
entityMappings:
- fieldMappings:
  - identifier: Address
    columnName: SrcIpAddress
  entityType: IP
eventGroupingSettings:
  aggregationKind: SingleAlert
triggerThreshold: 0
tactics:
- Impact
queryPeriod: 1h
customDetails:
  Edge_Name: EdgeName
incidentConfiguration:
  groupingConfiguration:
    enabled: true
    lookbackDuration: 1h
    groupByCustomDetails: []
    groupByAlertDetails: []
    reopenClosedIncident: false
    matchingMethod: AllEntities
    groupByEntities: []
  createIncident: true
relevantTechniques:
- T1498

ARM