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;
// Restrict unioned tables to the full analysis window to avoid full-table scans
let FullWindowStart = ago(StartLearningPeriod);
let FullWindowEnd = now();
let TrafficLogs = (union isfuzzy=true
(AzureDiagnostics
| where TimeGenerated between (FullWindowStart .. FullWindowEnd)
| 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
| where TimeGenerated between (FullWindowStart .. FullWindowEnd)
| extend Fqdn = DestinationIp
| where Action == "Deny"
| where isnotempty(Fqdn) and isnotempty(SourceIp)),
(AZFWFlowTrace
| where TimeGenerated between (FullWindowStart .. FullWindowEnd)
| extend Fqdn = DestinationIp
| where Action == "Deny"
| where isnotempty(Fqdn) and isnotempty(SourceIp)),
(AZFWIdpsSignature
| where TimeGenerated between (FullWindowStart .. FullWindowEnd)
| extend Fqdn = DestinationIp
| where Action == "Deny"
| where isnotempty(Fqdn) and isnotempty(SourceIp)),
(AZFWApplicationRule
| where TimeGenerated between (FullWindowStart .. FullWindowEnd)
| 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, Fqdn);
AlertTimeSrcIpDenyRate
| join kind=leftouter (LearningSrcIpDenyRate) on SourceIp, Fqdn
| extend LearningThreshold = max_of(LearningTimeSrcIpDenyRateAvg + NumOfStdsThreshold * LearningTimeSrcIpDenyRateStd, MinThreshold)
| where AlertTimeSrcIpDenyRateCount > LearningThreshold
| project SourceIp, Fqdn, AlertTimeSrcIpDenyRateCount, LearningTimeBuckets, LearningThreshold

triggerOperator: gt
id: d36bb1e3-5abc-4037-ad9a-24ba3469819e
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;
  // Restrict unioned tables to the full analysis window to avoid full-table scans
  let FullWindowStart = ago(StartLearningPeriod);
  let FullWindowEnd = now();
  let TrafficLogs = (union isfuzzy=true
  (AzureDiagnostics
  | where TimeGenerated between (FullWindowStart .. FullWindowEnd)
  | 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
  | where TimeGenerated between (FullWindowStart .. FullWindowEnd)
  | extend Fqdn = DestinationIp
  | where Action == "Deny"
  | where isnotempty(Fqdn) and isnotempty(SourceIp)),
  (AZFWFlowTrace
  | where TimeGenerated between (FullWindowStart .. FullWindowEnd)
  | extend Fqdn = DestinationIp
  | where Action == "Deny"
  | where isnotempty(Fqdn) and isnotempty(SourceIp)),
  (AZFWIdpsSignature
  | where TimeGenerated between (FullWindowStart .. FullWindowEnd)
  | extend Fqdn = DestinationIp
  | where Action == "Deny"
  | where isnotempty(Fqdn) and isnotempty(SourceIp)),
  (AZFWApplicationRule
  | where TimeGenerated between (FullWindowStart .. FullWindowEnd)
  | 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, Fqdn);
  AlertTimeSrcIpDenyRate
  | join kind=leftouter (LearningSrcIpDenyRate) on SourceIp, Fqdn
  | extend LearningThreshold = max_of(LearningTimeSrcIpDenyRateAvg + NumOfStdsThreshold * LearningTimeSrcIpDenyRateStd, MinThreshold)
  | where AlertTimeSrcIpDenyRateCount > LearningThreshold
  | project SourceIp, Fqdn, AlertTimeSrcIpDenyRateCount, LearningTimeBuckets, LearningThreshold
triggerThreshold: 0
tactics:
- InitialAccess
- Exfiltration
- CommandAndControl
- Discovery
name: Abnormal Deny Rate for Source IP
status: Available
customDetails:
  AlertCount: AlertTimeSrcIpDenyRateCount
  Threshold: LearningThreshold
queryFrequency: 1h
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.'
severity: Medium
alertDetailsOverride:
  alertDescriptionFormat: |
    The source IP {{SourceIp}} has an abnormal deny rate to destination {{Fqdn}} with {{AlertTimeSrcIpDenyRateCount}} denies, which is above the calculated threshold. This could indicate potential exfiltration, initial access or C2 activities.
  alertDisplayNameFormat: Abnormal Deny Rate for Source IP {{SourceIp}}
entityMappings:
- fieldMappings:
  - columnName: SourceIp
    identifier: Address
  entityType: IP
- fieldMappings:
  - columnName: Fqdn
    identifier: Url
  entityType: URL
kind: Scheduled
version: 1.1.3
requiredDataConnectors:
- connectorId: AzureFirewall
  dataTypes:
  - AzureDiagnostics
  - AZFWApplicationRule
  - AZFWNetworkRule
  - AZFWFlowTrace
  - AZFWIdpsSignature
relevantTechniques:
- T1190
- T1041
- T1568.001
- T1568.002
- T1046
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Azure%20Firewall/Analytic%20Rules/Azure%20Firewall%20-%20Abnormal%20Deny%20Rate%20for%20Source%20IP.yaml
queryPeriod: 25h

{
  "$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": {
        "alertDetailsOverride": {
          "alertDescriptionFormat": "The source IP {{SourceIp}} has an abnormal deny rate to destination {{Fqdn}} with {{AlertTimeSrcIpDenyRateCount}} denies, which is above the calculated threshold. This could indicate potential exfiltration, initial access or C2 activities.\n",
          "alertDisplayNameFormat": "Abnormal Deny Rate for Source IP {{SourceIp}}"
        },
        "alertRuleTemplateName": "d36bb1e3-5abc-4037-ad9a-24ba3469819e",
        "customDetails": {
          "AlertCount": "AlertTimeSrcIpDenyRateCount",
          "Threshold": "LearningThreshold"
        },
        "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%20Firewall/Analytic%20Rules/Azure%20Firewall%20-%20Abnormal%20Deny%20Rate%20for%20Source%20IP.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;\n// Restrict unioned tables to the full analysis window to avoid full-table scans\nlet FullWindowStart = ago(StartLearningPeriod);\nlet FullWindowEnd = now();\nlet TrafficLogs = (union isfuzzy=true\n(AzureDiagnostics\n| where TimeGenerated between (FullWindowStart .. FullWindowEnd)\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| where TimeGenerated between (FullWindowStart .. FullWindowEnd)\n| extend Fqdn = DestinationIp\n| where Action == \"Deny\"\n| where isnotempty(Fqdn) and isnotempty(SourceIp)),\n(AZFWFlowTrace\n| where TimeGenerated between (FullWindowStart .. FullWindowEnd)\n| extend Fqdn = DestinationIp\n| where Action == \"Deny\"\n| where isnotempty(Fqdn) and isnotempty(SourceIp)),\n(AZFWIdpsSignature\n| where TimeGenerated between (FullWindowStart .. FullWindowEnd)\n| extend Fqdn = DestinationIp\n| where Action == \"Deny\"\n| where isnotempty(Fqdn) and isnotempty(SourceIp)),\n(AZFWApplicationRule\n| where TimeGenerated between (FullWindowStart .. FullWindowEnd)\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, Fqdn);\nAlertTimeSrcIpDenyRate\n| join kind=leftouter (LearningSrcIpDenyRate) on SourceIp, Fqdn\n| extend LearningThreshold = max_of(LearningTimeSrcIpDenyRateAvg + NumOfStdsThreshold * LearningTimeSrcIpDenyRateStd, MinThreshold)\n| where AlertTimeSrcIpDenyRateCount > LearningThreshold\n| project SourceIp, Fqdn, AlertTimeSrcIpDenyRateCount, LearningTimeBuckets, LearningThreshold\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT25H",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [
          "T1568.001",
          "T1568.002"
        ],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl",
          "Discovery",
          "Exfiltration",
          "InitialAccess"
        ],
        "techniques": [
          "T1041",
          "T1046",
          "T1190",
          "T1568"
        ],
        "templateVersion": "1.1.3",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}