Abnormal Deny Rate for Source IP

let LearningPeriod = 1d;
let RunTime = 1h;
let StartLearningPeriod = LearningPeriod + RunTime;
let EndRunTime = RunTime - 1h;
let BinTime = 1h;
let NumOfStdsThreshold = 3;
let MinThreshold = 5.0;
let MinLearningBuckets = 5;
let TrafficLogs = (union isfuzzy=true
(AzureDiagnostics
| where OperationName == "AzureFirewallApplicationRuleLog" or OperationName == "AzureFirewallNetworkRuleLog" 
| parse msg_s with * "from " SourceIp ":" SourcePort:int " to " Fqdn ":" DestinationPort:int ". " * "Action: " Action "." *
| where Action == "Deny"
| where isnotempty(Fqdn) and isnotempty(SourceIp)),
(AZFWNetworkRule
| extend Fqdn = DestinationIp
| where Action == "Deny"
| where isnotempty(Fqdn) and isnotempty(SourceIp)),
(AZFWFlowTrace
| extend Fqdn = DestinationIp
| where Action == "Deny"
| where isnotempty(Fqdn) and isnotempty(SourceIp)),
(AZFWIdpsSignature
| extend Fqdn = DestinationIp
| where Action == "Deny"
| where isnotempty(Fqdn) and isnotempty(SourceIp)),
(AZFWApplicationRule
| where Action == "Deny"
| where isnotempty(Fqdn) and isnotempty(SourceIp)));
let LearningSrcIpDenyRate = (TrafficLogs
| where TimeGenerated between (ago(StartLearningPeriod) .. ago(RunTime))
| summarize count() by SourceIp, bin(TimeGenerated, BinTime), Fqdn
| summarize LearningTimeSrcIpDenyRateAvg = avg(count_), LearningTimeSrcIpDenyRateStd = stdev(count_), LearningTimeBuckets = count() by SourceIp, Fqdn
| where LearningTimeBuckets > MinLearningBuckets);
let AlertTimeSrcIpDenyRate = (TrafficLogs
| where TimeGenerated between (ago(RunTime) .. ago(EndRunTime))
| summarize AlertTimeSrcIpDenyRateCount = count() by SourceIp);
AlertTimeSrcIpDenyRate
| join kind=leftouter (LearningSrcIpDenyRate) on SourceIp
| extend LearningThreshold = max_of(LearningTimeSrcIpDenyRateAvg + NumOfStdsThreshold * LearningTimeSrcIpDenyRateStd, MinThreshold)
| where AlertTimeSrcIpDenyRateCount > LearningThreshold
| project-away SourceIp1, LearningTimeSrcIpDenyRateAvg, LearningTimeSrcIpDenyRateStd

relevantTechniques:
- T1190
- T1041
- T1568
name: Abnormal Deny Rate for Source IP
requiredDataConnectors:
- dataTypes:
  - AzureDiagnostics
  - AZFWApplicationRule
  - AZFWNetworkRule
  - AZFWFlowTrace
  - AZFWIdpsSignature
  connectorId: AzureFirewall
entityMappings:
- fieldMappings:
  - identifier: Address
    columnName: SourceIp
  entityType: IP
- fieldMappings:
  - identifier: Url
    columnName: Fqdn
  entityType: URL
triggerThreshold: 1
id: d36bb1e3-5abc-4037-ad9a-24ba3469819e
tactics:
- InitialAccess
- Exfiltration
- CommandAndControl
version: 1.1.2
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Azure Firewall/Analytic Rules/Azure Firewall - Abnormal Deny Rate for Source IP.yaml
queryPeriod: 25h
kind: Scheduled
queryFrequency: 1h
severity: Medium
status: Available
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 attacker tries to exploit the same vulnerability on machines in the organization, but is being blocked by firewall rules.

  Configurable Parameters:

  - Minimum of stds threshold - the number of stds to use in the threshold calculation. Default is set to 3.
  - Learning period time - learning period for threshold calculation in days. Default is set to 5.
  - Bin time - learning buckets time in hours. Default is set to 1 hour.
  - Minimum threshold - minimum threshold for alert. Default is set to 5.
  - Minimum bucket threshold - minimum learning buckets threshold for alert. Default is set to 5.'  
query: |
  let LearningPeriod = 1d;
  let RunTime = 1h;
  let StartLearningPeriod = LearningPeriod + RunTime;
  let EndRunTime = RunTime - 1h;
  let BinTime = 1h;
  let NumOfStdsThreshold = 3;
  let MinThreshold = 5.0;
  let MinLearningBuckets = 5;
  let TrafficLogs = (union isfuzzy=true
  (AzureDiagnostics
  | where OperationName == "AzureFirewallApplicationRuleLog" or OperationName == "AzureFirewallNetworkRuleLog" 
  | parse msg_s with * "from " SourceIp ":" SourcePort:int " to " Fqdn ":" DestinationPort:int ". " * "Action: " Action "." *
  | where Action == "Deny"
  | where isnotempty(Fqdn) and isnotempty(SourceIp)),
  (AZFWNetworkRule
  | extend Fqdn = DestinationIp
  | where Action == "Deny"
  | where isnotempty(Fqdn) and isnotempty(SourceIp)),
  (AZFWFlowTrace
  | extend Fqdn = DestinationIp
  | where Action == "Deny"
  | where isnotempty(Fqdn) and isnotempty(SourceIp)),
  (AZFWIdpsSignature
  | extend Fqdn = DestinationIp
  | where Action == "Deny"
  | where isnotempty(Fqdn) and isnotempty(SourceIp)),
  (AZFWApplicationRule
  | where Action == "Deny"
  | where isnotempty(Fqdn) and isnotempty(SourceIp)));
  let LearningSrcIpDenyRate = (TrafficLogs
  | where TimeGenerated between (ago(StartLearningPeriod) .. ago(RunTime))
  | summarize count() by SourceIp, bin(TimeGenerated, BinTime), Fqdn
  | summarize LearningTimeSrcIpDenyRateAvg = avg(count_), LearningTimeSrcIpDenyRateStd = stdev(count_), LearningTimeBuckets = count() by SourceIp, Fqdn
  | where LearningTimeBuckets > MinLearningBuckets);
  let AlertTimeSrcIpDenyRate = (TrafficLogs
  | where TimeGenerated between (ago(RunTime) .. ago(EndRunTime))
  | summarize AlertTimeSrcIpDenyRateCount = count() by SourceIp);
  AlertTimeSrcIpDenyRate
  | join kind=leftouter (LearningSrcIpDenyRate) on SourceIp
  | extend LearningThreshold = max_of(LearningTimeSrcIpDenyRateAvg + NumOfStdsThreshold * LearningTimeSrcIpDenyRateStd, MinThreshold)
  | where AlertTimeSrcIpDenyRateCount > LearningThreshold
  | project-away SourceIp1, LearningTimeSrcIpDenyRateAvg, LearningTimeSrcIpDenyRateStd  
triggerOperator: gt

{
  "$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/d36bb1e3-5abc-4037-ad9a-24ba3469819e')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/d36bb1e3-5abc-4037-ad9a-24ba3469819e')]",
      "properties": {
        "alertRuleTemplateName": "d36bb1e3-5abc-4037-ad9a-24ba3469819e",
        "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 attacker tries to exploit the same vulnerability on machines in the organization, but is being blocked by firewall rules.\n\nConfigurable Parameters:\n\n- Minimum of stds threshold - the number of stds to use in the threshold calculation. Default is set to 3.\n- Learning period time - learning period for threshold calculation in days. Default is set to 5.\n- Bin time - learning buckets time in hours. Default is set to 1 hour.\n- Minimum threshold - minimum threshold for alert. Default is set to 5.\n- Minimum bucket threshold - minimum learning buckets threshold for alert. Default is set to 5.'\n",
        "displayName": "Abnormal Deny Rate for Source IP",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "SourceIp",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "URL",
            "fieldMappings": [
              {
                "columnName": "Fqdn",
                "identifier": "Url"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Azure Firewall/Analytic Rules/Azure Firewall - Abnormal Deny Rate for Source IP.yaml",
        "query": "let LearningPeriod = 1d;\nlet RunTime = 1h;\nlet StartLearningPeriod = LearningPeriod + RunTime;\nlet EndRunTime = RunTime - 1h;\nlet BinTime = 1h;\nlet NumOfStdsThreshold = 3;\nlet MinThreshold = 5.0;\nlet MinLearningBuckets = 5;\nlet TrafficLogs = (union isfuzzy=true\n(AzureDiagnostics\n| where OperationName == \"AzureFirewallApplicationRuleLog\" or OperationName == \"AzureFirewallNetworkRuleLog\" \n| parse msg_s with * \"from \" SourceIp \":\" SourcePort:int \" to \" Fqdn \":\" DestinationPort:int \". \" * \"Action: \" Action \".\" *\n| where Action == \"Deny\"\n| where isnotempty(Fqdn) and isnotempty(SourceIp)),\n(AZFWNetworkRule\n| extend Fqdn = DestinationIp\n| where Action == \"Deny\"\n| where isnotempty(Fqdn) and isnotempty(SourceIp)),\n(AZFWFlowTrace\n| extend Fqdn = DestinationIp\n| where Action == \"Deny\"\n| where isnotempty(Fqdn) and isnotempty(SourceIp)),\n(AZFWIdpsSignature\n| extend Fqdn = DestinationIp\n| where Action == \"Deny\"\n| where isnotempty(Fqdn) and isnotempty(SourceIp)),\n(AZFWApplicationRule\n| where Action == \"Deny\"\n| where isnotempty(Fqdn) and isnotempty(SourceIp)));\nlet LearningSrcIpDenyRate = (TrafficLogs\n| where TimeGenerated between (ago(StartLearningPeriod) .. ago(RunTime))\n| summarize count() by SourceIp, bin(TimeGenerated, BinTime), Fqdn\n| summarize LearningTimeSrcIpDenyRateAvg = avg(count_), LearningTimeSrcIpDenyRateStd = stdev(count_), LearningTimeBuckets = count() by SourceIp, Fqdn\n| where LearningTimeBuckets > MinLearningBuckets);\nlet AlertTimeSrcIpDenyRate = (TrafficLogs\n| where TimeGenerated between (ago(RunTime) .. ago(EndRunTime))\n| summarize AlertTimeSrcIpDenyRateCount = count() by SourceIp);\nAlertTimeSrcIpDenyRate\n| join kind=leftouter (LearningSrcIpDenyRate) on SourceIp\n| extend LearningThreshold = max_of(LearningTimeSrcIpDenyRateAvg + NumOfStdsThreshold * LearningTimeSrcIpDenyRateStd, MinThreshold)\n| where AlertTimeSrcIpDenyRateCount > LearningThreshold\n| project-away SourceIp1, LearningTimeSrcIpDenyRateAvg, LearningTimeSrcIpDenyRateStd\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT25H",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl",
          "Exfiltration",
          "InitialAccess"
        ],
        "techniques": [
          "T1041",
          "T1190",
          "T1568"
        ],
        "templateVersion": "1.1.2",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 1
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}