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

severity: Medium
tactics:
- InitialAccess
- Exfiltration
- CommandAndControl
- Discovery
queryFrequency: 1h
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
entityMappings:
- fieldMappings:
  - identifier: Address
    columnName: SourceIp
  entityType: IP
- fieldMappings:
  - identifier: Url
    columnName: Fqdn
  entityType: URL
customDetails:
  AlertCount: AlertTimeSrcIpDenyRateCount
  Threshold: LearningThreshold
kind: Scheduled
triggerOperator: gt
name: Abnormal Deny Rate for Source IP
version: 1.1.3
status: Available
requiredDataConnectors:
- dataTypes:
  - AzureDiagnostics
  - AZFWApplicationRule
  - AZFWNetworkRule
  - AZFWFlowTrace
  - AZFWIdpsSignature
  connectorId: AzureFirewall
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.'
relevantTechniques:
- T1190
- T1041
- T1568.001
- T1568.002
- T1046
queryPeriod: 25h
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Azure%20Firewall/Analytic%20Rules/Azure%20Firewall%20-%20Abnormal%20Deny%20Rate%20for%20Source%20IP.yaml
triggerThreshold: 0
alertDetailsOverride:
  alertDisplayNameFormat: Abnormal Deny Rate for Source IP {{SourceIp}}
  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.

{
  "$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"
    }
  ]
}