Detect instances of multiple client errors occurring within a brief period of time ASIM Web Session

// HTTP response status codes indicate whether a specific HTTP request has been successfully completed.
// Please refer this for more details: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status
let threshold = 100; // You can set threshold value that suits your environment
_Im_WebSession(starttime=ago(1h))
| where toint(EventResultDetails) between (400 .. 499)
| summarize
    TotalErrorCount = count(),
    EventStartTime = min(TimeGenerated),
    EventEndTime = max(TimeGenerated),
    URLs=make_set(Url, 100),
    EventResultDetailsSet=make_set(EventResultDetails,10)
    by SrcIpAddr, bin(TimeGenerated, 5m), SrcUsername, SrcHostname
| where TotalErrorCount > threshold
| extend Name = iif(SrcUsername contains "@", tostring(split(SrcUsername,'@',0)[0]),SrcUsername), UPNSuffix = iif(SrcUsername contains "@",tostring(split(SrcUsername,'@',1)[0]),""), Threshold=threshold

status: Available
queryFrequency: 1h
tags:
- Schema: WebSession
  SchemaVersion: 0.2.6
queryPeriod: 1h
kind: Scheduled
version: 1.0.0
triggerThreshold: 0
relevantTechniques:
- T1190
- T1133
- T1071
description: |
    'This detection mechanism identifies situations where multiple client errors originate from a single source within a limited time frame.'
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Web Session Essentials/Analytic Rules/MultipleClientErrorsWithinShortTime.yaml
customDetails:
  EventResultSet: EventResultDetailsSet
  ErrorThreshold: Threshold
  EventStartTime: EventStartTime
  RequestURLs: URLs
  EventEndTime: EventEndTime
  TotalErrorCount: TotalErrorCount
requiredDataConnectors: []
id: faa40333-1e8b-40cc-a003-51ae41fa886f
alertDetailsOverride:
  alertDisplayNameFormat: High number of client errors originated by user '{{SrcUsername}}' from IP address '{{SrcIpAddr}}'
  alertDescriptionFormat: "The client has made a total of '{{TotalErrorCount}}' requests to URLs '{{URLs}}', which have resulted in client errors. A sudden surge in HTTP code errors, especially in the form of client-side errors like 400 or 401, could indicate malicious activity, such as attackers attempting to exploit vulnerabilities or perform unauthorized actions. For detailed information regarding the specific errors encountered, please refer to the following link: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status."
name: Detect instances of multiple client errors occurring within a brief period of time (ASIM Web Session)
triggerOperator: gt
tactics:
- InitialAccess
- CommandAndControl
eventGroupingSettings:
  aggregationKind: AlertPerResult
query: |
  // HTTP response status codes indicate whether a specific HTTP request has been successfully completed.
  // Please refer this for more details: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status
  let threshold = 100; // You can set threshold value that suits your environment
  _Im_WebSession(starttime=ago(1h))
  | where toint(EventResultDetails) between (400 .. 499)
  | summarize
      TotalErrorCount = count(),
      EventStartTime = min(TimeGenerated),
      EventEndTime = max(TimeGenerated),
      URLs=make_set(Url, 100),
      EventResultDetailsSet=make_set(EventResultDetails,10)
      by SrcIpAddr, bin(TimeGenerated, 5m), SrcUsername, SrcHostname
  | where TotalErrorCount > threshold
  | extend Name = iif(SrcUsername contains "@", tostring(split(SrcUsername,'@',0)[0]),SrcUsername), UPNSuffix = iif(SrcUsername contains "@",tostring(split(SrcUsername,'@',1)[0]),""), Threshold=threshold  
entityMappings:
- fieldMappings:
  - identifier: Address
    columnName: SrcIpAddr
  entityType: IP
- fieldMappings:
  - identifier: Name
    columnName: Name
  - identifier: UPNSuffix
    columnName: UPNSuffix
  entityType: Account
- fieldMappings:
  - identifier: HostName
    columnName: SrcHostname
  entityType: Host
severity: Medium