GSA - Detect Abnormal Deny Rate for Source to Destination IP

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Id	e3b6a9e7-4c3a-45e6-8baf-1d3bfa8e0c2b
Rulename	GSA - Detect Abnormal Deny Rate for Source to Destination IP
Description	Identifies abnormal deny rate for specific source IP to destination IP based on the normal average and standard deviation learned during a configured period. This can indicate potential exfiltration, initial access, or C2, where an attacker tries to exploit the same vulnerability on machines in the organization but is being blocked by firewall rules.
Severity	Medium
Tactics	InitialAccess Exfiltration CommandAndControl
Techniques	T1571
Required data connectors	AzureActiveDirectory
Kind	Scheduled
Query frequency	1h
Query period	7d
Trigger threshold	1
Trigger operator	gt
Source Uri	https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Global%20Secure%20Access/Analytic%20Rules/SWG%20-%20Abnormal%20Deny%20Rate.yaml
Version	1.0.5
Arm template	e3b6a9e7-4c3a-45e6-8baf-1d3bfa8e0c2b.json

KQL

let NumOfStdsThreshold = 3;
let LearningPeriod = 5d;
let BinTime = 1h;
let MinThreshold = 5.0;
let MinLearningBuckets = 5;
let TrafficLogs = NetworkAccessTraffic
  | where Action == "Denied"
  | where isnotempty(DestinationIp) and isnotempty(SourceIp);
let LearningSrcIpDenyRate = TrafficLogs
  | where TimeGenerated between (ago(LearningPeriod + 1d) .. ago(1d))
  | summarize count_ = count() by SourceIp, bin(TimeGenerated, BinTime), DestinationIp
  | summarize LearningTimeSrcIpDenyRateAvg = avg(count_), LearningTimeSrcIpDenyRateStd = stdev(count_), LearningTimeBuckets = count() by SourceIp, DestinationIp
  | where LearningTimeBuckets > MinLearningBuckets;
let AlertTimeSrcIpDenyRate = TrafficLogs
  | where TimeGenerated between (ago(1h) .. now())
  | summarize AlertTimeSrcIpDenyRateCount = count() by SourceIp, DestinationIp;
AlertTimeSrcIpDenyRate
  | join kind=leftouter (LearningSrcIpDenyRate) on SourceIp, DestinationIp
  | extend LearningThreshold = max_of(LearningTimeSrcIpDenyRateAvg + NumOfStdsThreshold * LearningTimeSrcIpDenyRateStd, MinThreshold)
  | where AlertTimeSrcIpDenyRateCount > LearningThreshold
  | project SourceIp, DestinationIp, AlertTimeSrcIpDenyRateCount, LearningThreshold

YAML

queryFrequency: 1h
entityMappings:
- fieldMappings:
  - columnName: SourceIp
    identifier: Address
  entityType: IP
- fieldMappings:
  - columnName: DestinationIp
    identifier: Address
  entityType: IP
triggerThreshold: 1
triggerOperator: gt
severity: Medium
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Global%20Secure%20Access/Analytic%20Rules/SWG%20-%20Abnormal%20Deny%20Rate.yaml
query: |
  let NumOfStdsThreshold = 3;
  let LearningPeriod = 5d;
  let BinTime = 1h;
  let MinThreshold = 5.0;
  let MinLearningBuckets = 5;
  let TrafficLogs = NetworkAccessTraffic
    | where Action == "Denied"
    | where isnotempty(DestinationIp) and isnotempty(SourceIp);
  let LearningSrcIpDenyRate = TrafficLogs
    | where TimeGenerated between (ago(LearningPeriod + 1d) .. ago(1d))
    | summarize count_ = count() by SourceIp, bin(TimeGenerated, BinTime), DestinationIp
    | summarize LearningTimeSrcIpDenyRateAvg = avg(count_), LearningTimeSrcIpDenyRateStd = stdev(count_), LearningTimeBuckets = count() by SourceIp, DestinationIp
    | where LearningTimeBuckets > MinLearningBuckets;
  let AlertTimeSrcIpDenyRate = TrafficLogs
    | where TimeGenerated between (ago(1h) .. now())
    | summarize AlertTimeSrcIpDenyRateCount = count() by SourceIp, DestinationIp;
  AlertTimeSrcIpDenyRate
    | join kind=leftouter (LearningSrcIpDenyRate) on SourceIp, DestinationIp
    | extend LearningThreshold = max_of(LearningTimeSrcIpDenyRateAvg + NumOfStdsThreshold * LearningTimeSrcIpDenyRateStd, MinThreshold)
    | where AlertTimeSrcIpDenyRateCount > LearningThreshold
    | project SourceIp, DestinationIp, AlertTimeSrcIpDenyRateCount, LearningThreshold
tactics:
- InitialAccess
- Exfiltration
- CommandAndControl
queryPeriod: 7d
relevantTechniques:
- T1571
requiredDataConnectors:
- connectorId: AzureActiveDirectory
  dataTypes:
  - NetworkAccessTrafficLogs
id: e3b6a9e7-4c3a-45e6-8baf-1d3bfa8e0c2b
kind: Scheduled
version: 1.0.5
description: |
  Identifies abnormal deny rate for specific source IP to destination IP based on the normal average and standard deviation learned during a configured period. This can indicate potential exfiltration, initial access, or C2, where an attacker tries to exploit the same vulnerability on machines in the organization but is being blocked by firewall rules.
status: Available
name: GSA - Detect Abnormal Deny Rate for Source to Destination IP

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/e3b6a9e7-4c3a-45e6-8baf-1d3bfa8e0c2b')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/e3b6a9e7-4c3a-45e6-8baf-1d3bfa8e0c2b')]",
      "properties": {
        "alertRuleTemplateName": "e3b6a9e7-4c3a-45e6-8baf-1d3bfa8e0c2b",
        "customDetails": null,
        "description": "Identifies abnormal deny rate for specific source IP to destination IP based on the normal average and standard deviation learned during a configured period. This can indicate potential exfiltration, initial access, or C2, where an attacker tries to exploit the same vulnerability on machines in the organization but is being blocked by firewall rules.\n",
        "displayName": "GSA - Detect Abnormal Deny Rate for Source to Destination IP",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SourceIp",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "DestinationIp",
                "identifier": "Address"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Global%20Secure%20Access/Analytic%20Rules/SWG%20-%20Abnormal%20Deny%20Rate.yaml",
        "query": "let NumOfStdsThreshold = 3;\nlet LearningPeriod = 5d;\nlet BinTime = 1h;\nlet MinThreshold = 5.0;\nlet MinLearningBuckets = 5;\nlet TrafficLogs = NetworkAccessTraffic\n  | where Action == \"Denied\"\n  | where isnotempty(DestinationIp) and isnotempty(SourceIp);\nlet LearningSrcIpDenyRate = TrafficLogs\n  | where TimeGenerated between (ago(LearningPeriod + 1d) .. ago(1d))\n  | summarize count_ = count() by SourceIp, bin(TimeGenerated, BinTime), DestinationIp\n  | summarize LearningTimeSrcIpDenyRateAvg = avg(count_), LearningTimeSrcIpDenyRateStd = stdev(count_), LearningTimeBuckets = count() by SourceIp, DestinationIp\n  | where LearningTimeBuckets > MinLearningBuckets;\nlet AlertTimeSrcIpDenyRate = TrafficLogs\n  | where TimeGenerated between (ago(1h) .. now())\n  | summarize AlertTimeSrcIpDenyRateCount = count() by SourceIp, DestinationIp;\nAlertTimeSrcIpDenyRate\n  | join kind=leftouter (LearningSrcIpDenyRate) on SourceIp, DestinationIp\n  | extend LearningThreshold = max_of(LearningTimeSrcIpDenyRateAvg + NumOfStdsThreshold * LearningTimeSrcIpDenyRateStd, MinThreshold)\n  | where AlertTimeSrcIpDenyRateCount > LearningThreshold\n  | project SourceIp, DestinationIp, AlertTimeSrcIpDenyRateCount, LearningThreshold\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "P7D",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl",
          "Exfiltration",
          "InitialAccess"
        ],
        "techniques": [
          "T1571"
        ],
        "templateVersion": "1.0.5",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 1
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}