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. 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 CiscoAsaAma CiscoMeraki Corelight Fortinet MicrosoftSysmonForLinux MicrosoftThreatProtection PaloAltoNetworks SecurityEvents WindowsForwardedEvents WindowsSecurityEvents 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	1.2.7
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

requiredDataConnectors:
- connectorId: AWSS3
  dataTypes:
  - AWSVPCFlow
- connectorId: MicrosoftThreatProtection
  dataTypes:
  - DeviceNetworkEvents
- connectorId: SecurityEvents
  dataTypes:
  - SecurityEvent
- connectorId: WindowsSecurityEvents
  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: CiscoAsaAma
  dataTypes:
  - CommonSecurityLog
- connectorId: Corelight
  dataTypes:
  - Corelight_CL
- connectorId: AIVectraStream
  dataTypes:
  - VectraStream
- connectorId: CheckPoint
  dataTypes:
  - CommonSecurityLog
- connectorId: Fortinet
  dataTypes:
  - CommonSecurityLog
- connectorId: CiscoMeraki
  dataTypes:
  - Syslog
  - CiscoMerakiNativePoller
status: Available
relevantTechniques:
- T1499
queryFrequency: 1h
id: 4902eddb-34f7-44a8-ac94-8486366e9494
customDetails:
  NumberOfDenies: Count
name: Excessive number of failed connections from a single source (ASIM Network Session schema)
severity: Medium
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Network Session Essentials/Analytic Rules/ExcessiveHTTPFailuresFromSource.yaml
queryPeriod: 1h
entityMappings:
- fieldMappings:
  - columnName: SrcIpAddr
    identifier: Address
  entityType: IP
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.
   This analytic rule uses [ASIM](https://aka.ms/AboutASIM) and supports any built-in or custom source that supports the ASIM NetworkSession schema'  
triggerThreshold: 0
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
query: |
  let threshold = 5000;
  _Im_NetworkSession(eventresult='Failure')
  | summarize Count=count() by SrcIpAddr, bin(TimeGenerated,5m)
  | where Count > threshold
  | extend timestamp = TimeGenerated, threshold  
kind: Scheduled
triggerOperator: gt
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: 1.2.7

ARM

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2024-01-01-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.\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",
        "subTechniques": [],
        "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": "1.2.7",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}