Excessive number of failed connections from a single source ASIM Network Session schema

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Id	4902eddb-34f7-44a8-ac94-8486366e9494
Rulename	Excessive number of failed connections from a single source (ASIM Network Session schema)
Description	This rule identifies a single source that generates an excessive amount of failed connections. Modify the threshold to change the sensitivity of the rule: the higher the threshold, the less sensitive is the rule and less incidents will be generated.<br><br> This analytic rule uses ASIM and supports any built-in or custom source that supports the ASIM NetworkSession schema
Severity	Medium
Tactics	Impact
Techniques	T1499
Required data connectors	AIVectraStream AWSS3 AzureFirewall AzureMonitor(VMInsights) AzureNSG CheckPoint CiscoASA CiscoMeraki Corelight Fortinet MicrosoftSysmonForLinux MicrosoftThreatProtection PaloAltoNetworks SecurityEvents WindowsForwardedEvents Zscaler
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/Network Session Essentials/Analytic Rules/ExcessiveHTTPFailuresFromSource.yaml
Version	1.2.5
Arm template	4902eddb-34f7-44a8-ac94-8486366e9494.json

KQL

let threshold = 5000;
_Im_NetworkSession(eventresult='Failure')
| summarize Count=count() by SrcIpAddr, bin(TimeGenerated,5m)
| where Count > threshold
| extend timestamp = TimeGenerated, threshold

YAML

customDetails:
  NumberOfDenies: Count
triggerOperator: gt
queryFrequency: 1h
description: |
  'This rule identifies a single source that generates an excessive amount of failed connections. Modify the threshold to change the sensitivity of the rule: the higher the threshold, the less sensitive is the rule and less incidents will be generated.<br><br> 
   This analytic rule uses [ASIM](https://aka.ms/AboutASIM) and supports any built-in or custom source that supports the ASIM NetworkSession schema'  
alertDetailsOverride:
  alertDescriptionFormat: The client at address {{SrcIpAddr}} generated more than {{threshold}} failures over a 5 minutes time window, which may indicate malicious activity.
  alertDisplayNameFormat: Excessive number of failed connections from {{SrcIpAddr}}
status: Available
kind: Scheduled
triggerThreshold: 0
requiredDataConnectors:
- connectorId: AWSS3
  dataTypes:
  - AWSVPCFlow
- connectorId: MicrosoftThreatProtection
  dataTypes:
  - DeviceNetworkEvents
- connectorId: SecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsForwardedEvents
  dataTypes:
  - WindowsEvent
- connectorId: Zscaler
  dataTypes:
  - CommonSecurityLog
- connectorId: MicrosoftSysmonForLinux
  dataTypes:
  - Syslog
- connectorId: PaloAltoNetworks
  dataTypes:
  - CommonSecurityLog
- connectorId: AzureMonitor(VMInsights)
  dataTypes:
  - VMConnection
- connectorId: AzureFirewall
  dataTypes:
  - AzureDiagnostics
- connectorId: AzureNSG
  dataTypes:
  - AzureDiagnostics
- connectorId: CiscoASA
  dataTypes:
  - CommonSecurityLog
- connectorId: Corelight
  dataTypes:
  - Corelight_CL
- connectorId: AIVectraStream
  dataTypes:
  - VectraStream
- connectorId: CheckPoint
  dataTypes:
  - CommonSecurityLog
- connectorId: Fortinet
  dataTypes:
  - CommonSecurityLog
- connectorId: CiscoMeraki
  dataTypes:
  - Syslog
  - CiscoMerakiNativePoller
version: 1.2.5
queryPeriod: 1h
name: Excessive number of failed connections from a single source (ASIM Network Session schema)
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Network Session Essentials/Analytic Rules/ExcessiveHTTPFailuresFromSource.yaml
id: 4902eddb-34f7-44a8-ac94-8486366e9494
tags:
- ParentAlert: https://github.com/Azure/Azure-Sentinel/tree/master/Solutions/Sophos%20XG%20Firewall/Analytic%20Rules/ExcessiveAmountofDeniedConnectionsfromASingleSource.yaml
  version: 1.0.0
- Schema: ASimNetworkSessions
  SchemaVersion: 0.2.4
tactics:
- Impact
relevantTechniques:
- T1499
severity: Medium
entityMappings:
- fieldMappings:
  - identifier: Address
    columnName: SrcIpAddr
  entityType: IP
query: |
  let threshold = 5000;
  _Im_NetworkSession(eventresult='Failure')
  | summarize Count=count() by SrcIpAddr, bin(TimeGenerated,5m)
  | where Count > threshold
  | extend timestamp = TimeGenerated, threshold

ARM

{
  "$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/4902eddb-34f7-44a8-ac94-8486366e9494')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/4902eddb-34f7-44a8-ac94-8486366e9494')]",
      "properties": {
        "alertDetailsOverride": {
          "alertDescriptionFormat": "The client at address {{SrcIpAddr}} generated more than {{threshold}} failures over a 5 minutes time window, which may indicate malicious activity.",
          "alertDisplayNameFormat": "Excessive number of failed connections from {{SrcIpAddr}}"
        },
        "alertRuleTemplateName": "4902eddb-34f7-44a8-ac94-8486366e9494",
        "customDetails": {
          "NumberOfDenies": "Count"
        },
        "description": "'This rule identifies a single source that generates an excessive amount of failed connections. Modify the threshold to change the sensitivity of the rule: the higher the threshold, the less sensitive is the rule and less incidents will be generated.<br><br> \n This analytic rule uses [ASIM](https://aka.ms/AboutASIM) and supports any built-in or custom source that supports the ASIM NetworkSession schema'\n",
        "displayName": "Excessive number of failed connections from a single source (ASIM Network Session schema)",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SrcIpAddr",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Network Session Essentials/Analytic Rules/ExcessiveHTTPFailuresFromSource.yaml",
        "query": "let threshold = 5000;\n_Im_NetworkSession(eventresult='Failure')\n| summarize Count=count() by SrcIpAddr, bin(TimeGenerated,5m)\n| where Count > threshold\n| extend timestamp = TimeGenerated, threshold\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "Impact"
        ],
        "tags": [
          {
            "ParentAlert": "https://github.com/Azure/Azure-Sentinel/tree/master/Solutions/Sophos%20XG%20Firewall/Analytic%20Rules/ExcessiveAmountofDeniedConnectionsfromASingleSource.yaml",
            "version": "1.0.0"
          },
          {
            "Schema": "ASimNetworkSessions",
            "SchemaVersion": "0.2.4"
          }
        ],
        "techniques": [
          "T1499"
        ],
        "templateVersion": "1.2.5",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}