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

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

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"
    }
  ]
}