App Gateway WAF - XSS Detection

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Id	1c7ff502-2ad4-4970-9d29-9210c6753138
Rulename	App Gateway WAF - XSS Detection
Description	Identifies a match for an XSS attack in the App Gateway WAF logs. The threshold value in the query can be changed as per your infrastructure’s requirements. References: https://owasp.org/www-community/attacks/xss/
Severity	High
Tactics	InitialAccess Execution
Techniques	T1189 T1203 T0853
Required data connectors	WAF
Kind	Scheduled
Query frequency	6h
Query period	6h
Trigger threshold	0
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Azure Web Application Firewall (WAF)/Analytic Rules/App-GW-WAF-XSSDetection.yaml
Version	1.0.2
Arm template	1c7ff502-2ad4-4970-9d29-9210c6753138.json

KQL

let Threshold = 3;  
AGWFirewallLogs
| where Action == "Matched"
| where Message has "XSS"
| project TransactionId, Hostname, RequestUri, TimeGenerated, ClientIp, Message
| join kind = inner(
AGWFirewallLogs
| where Action == "Blocked"
| extend transactionId_g = tostring(TransactionId)) on TransactionId
| extend Uri = strcat(Hostname,RequestUri)
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), TransactionID = make_set(transactionId_g,100), Message = make_set(Message,100), Total_TransactionId = dcount(transactionId_g) by ClientIp, Uri, Action
| where Total_TransactionId >= Threshold

YAML

description: |
  'Identifies a match for an XSS attack in the App Gateway WAF logs. The threshold value in the query can be changed as per your infrastructure's requirements.
   References: https://owasp.org/www-community/attacks/xss/'  
version: 1.0.2
triggerThreshold: 0
tactics:
- InitialAccess
- Execution
queryPeriod: 6h
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Azure Web Application Firewall (WAF)/Analytic Rules/App-GW-WAF-XSSDetection.yaml
triggerOperator: gt
status: Available
id: 1c7ff502-2ad4-4970-9d29-9210c6753138
name: App Gateway WAF - XSS Detection
queryFrequency: 6h
severity: High
kind: Scheduled
entityMappings:
- fieldMappings:
  - columnName: Uri
    identifier: Url
  entityType: URL
- fieldMappings:
  - columnName: ClientIp
    identifier: Address
  entityType: IP
relevantTechniques:
- T1189
- T1203
- T0853
query: |
  let Threshold = 3;  
  AGWFirewallLogs
  | where Action == "Matched"
  | where Message has "XSS"
  | project TransactionId, Hostname, RequestUri, TimeGenerated, ClientIp, Message
  | join kind = inner(
  AGWFirewallLogs
  | where Action == "Blocked"
  | extend transactionId_g = tostring(TransactionId)) on TransactionId
  | extend Uri = strcat(Hostname,RequestUri)
  | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), TransactionID = make_set(transactionId_g,100), Message = make_set(Message,100), Total_TransactionId = dcount(transactionId_g) by ClientIp, Uri, Action
  | where Total_TransactionId >= Threshold  
tags:
- Cross Site Scripting
requiredDataConnectors:
- dataTypes:
  - AzureDiagnostics
  connectorId: WAF

ARM