New UserAgent observed in last 24 hours

let starttime = 14d;
let endtime = 1d;
let UserAgentAll =
(union isfuzzy=true
(OfficeActivity
| where TimeGenerated >= ago(starttime)
| where isnotempty(UserAgent)
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent, SourceIP = ClientIP, Account = UserId, Type, RecordType, Operation
),
(
W3CIISLog
| where TimeGenerated >= ago(starttime)
| where isnotempty(csUserAgent)
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent = csUserAgent, SourceIP = cIP, Account = csUserName, Type, sSiteName, csMethod, csUriStem
),
(
AWSCloudTrail
| where TimeGenerated >= ago(starttime)
| where isnotempty(UserAgent)
| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent, SourceIP = SourceIpAddress, Account = UserIdentityUserName, Type, EventSource, EventName
))
// remove wordSize blocks of non-numeric hex characters prior to word extraction
| extend UserAgentNoHexAlphas = replace("([A-Fa-f]{4,})", "x", UserAgent)
// once blocks of hex chars are removed, extract wordSize blocks of a-z
| extend Tokens = extract_all("([A-Za-z]{4,})", UserAgentNoHexAlphas)
// concatenate extracted words to create a summarized user agent for baseline and comparison
| extend NormalizedUserAgent = strcat_array(Tokens, "|")
| project-away UserAgentNoHexAlphas, Tokens;
UserAgentAll
| where StartTime >= ago(endtime)
| summarize StartTime = min(StartTime), EndTime = max(EndTime), count() by UserAgent, NormalizedUserAgent, SourceIP, Account, Type, RecordType, Operation, EventSource, EventName, sSiteName, csMethod, csUriStem
| join kind=leftanti
(
UserAgentAll
| where StartTime < ago(endtime)
| summarize by NormalizedUserAgent, SourceIP, Account, Type, RecordType, Operation, EventSource, EventName, sSiteName, csMethod, csUriStem
)
on NormalizedUserAgent
| extend timestamp = StartTime, IPCustomEntity = SourceIP, AccountCustomEntity = Account

queryPeriod: 14d
version: 1.0.2
relevantTechniques:
- T1189
- T1071
- T1203
queryFrequency: 1d
kind: Scheduled
name: New UserAgent observed in last 24 hours
id: b725d62c-eb77-42ff-96f6-bdc6745fc6e0
entityMappings:
- fieldMappings:
  - columnName: AccountCustomEntity
    identifier: FullName
  entityType: Account
- fieldMappings:
  - columnName: IPCustomEntity
    identifier: Address
  entityType: IP
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Network Threat Protection Essentials/Analytic Rules/NewUserAgentLast24h.yaml
severity: Low
query: |
  let starttime = 14d;
  let endtime = 1d;
  let UserAgentAll =
  (union isfuzzy=true
  (OfficeActivity
  | where TimeGenerated >= ago(starttime)
  | where isnotempty(UserAgent)
  | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent, SourceIP = ClientIP, Account = UserId, Type, RecordType, Operation
  ),
  (
  W3CIISLog
  | where TimeGenerated >= ago(starttime)
  | where isnotempty(csUserAgent)
  | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent = csUserAgent, SourceIP = cIP, Account = csUserName, Type, sSiteName, csMethod, csUriStem
  ),
  (
  AWSCloudTrail
  | where TimeGenerated >= ago(starttime)
  | where isnotempty(UserAgent)
  | summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent, SourceIP = SourceIpAddress, Account = UserIdentityUserName, Type, EventSource, EventName
  ))
  // remove wordSize blocks of non-numeric hex characters prior to word extraction
  | extend UserAgentNoHexAlphas = replace("([A-Fa-f]{4,})", "x", UserAgent)
  // once blocks of hex chars are removed, extract wordSize blocks of a-z
  | extend Tokens = extract_all("([A-Za-z]{4,})", UserAgentNoHexAlphas)
  // concatenate extracted words to create a summarized user agent for baseline and comparison
  | extend NormalizedUserAgent = strcat_array(Tokens, "|")
  | project-away UserAgentNoHexAlphas, Tokens;
  UserAgentAll
  | where StartTime >= ago(endtime)
  | summarize StartTime = min(StartTime), EndTime = max(EndTime), count() by UserAgent, NormalizedUserAgent, SourceIP, Account, Type, RecordType, Operation, EventSource, EventName, sSiteName, csMethod, csUriStem
  | join kind=leftanti
  (
  UserAgentAll
  | where StartTime < ago(endtime)
  | summarize by NormalizedUserAgent, SourceIP, Account, Type, RecordType, Operation, EventSource, EventName, sSiteName, csMethod, csUriStem
  )
  on NormalizedUserAgent
  | extend timestamp = StartTime, IPCustomEntity = SourceIP, AccountCustomEntity = Account  
tactics:
- InitialAccess
- CommandAndControl
- Execution
description: |
  'Identifies new UserAgents observed in the last 24 hours versus the previous 14 days. This detection
  extracts words from user agents to build the baseline and determine rareity rather than perform a
  direct comparison. This avoids FPs caused by version numbers and other high entropy user agent components.
  These new UserAgents could be benign. However, in normally stable environments,
  these new UserAgents could provide a starting point for investigating malicious activity.
  Note: W3CIISLog can be noisy depending on the environment, however OfficeActivity and AWSCloudTrail are
  usually stable with low numbers of detections.'  
requiredDataConnectors:
- connectorId: AWS
  dataTypes:
  - AWSCloudTrail
- connectorId: Office365
  dataTypes:
  - OfficeActivity
- connectorId: AzureMonitor(IIS)
  dataTypes:
  - W3CIISLog
metadata:
  author:
    name: Shain
  source:
    kind: Community
  categories:
    domains:
    - Security - Others
  support:
    tier: Community
status: Available
triggerThreshold: 0
triggerOperator: gt

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/b725d62c-eb77-42ff-96f6-bdc6745fc6e0')]",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/b725d62c-eb77-42ff-96f6-bdc6745fc6e0')]",
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules",
      "kind": "Scheduled",
      "apiVersion": "2022-11-01",
      "properties": {
        "displayName": "New UserAgent observed in last 24 hours",
        "description": "'Identifies new UserAgents observed in the last 24 hours versus the previous 14 days. This detection\nextracts words from user agents to build the baseline and determine rareity rather than perform a\ndirect comparison. This avoids FPs caused by version numbers and other high entropy user agent components.\nThese new UserAgents could be benign. However, in normally stable environments,\nthese new UserAgents could provide a starting point for investigating malicious activity.\nNote: W3CIISLog can be noisy depending on the environment, however OfficeActivity and AWSCloudTrail are\nusually stable with low numbers of detections.'\n",
        "severity": "Low",
        "enabled": true,
        "query": "let starttime = 14d;\nlet endtime = 1d;\nlet UserAgentAll =\n(union isfuzzy=true\n(OfficeActivity\n| where TimeGenerated >= ago(starttime)\n| where isnotempty(UserAgent)\n| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent, SourceIP = ClientIP, Account = UserId, Type, RecordType, Operation\n),\n(\nW3CIISLog\n| where TimeGenerated >= ago(starttime)\n| where isnotempty(csUserAgent)\n| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent = csUserAgent, SourceIP = cIP, Account = csUserName, Type, sSiteName, csMethod, csUriStem\n),\n(\nAWSCloudTrail\n| where TimeGenerated >= ago(starttime)\n| where isnotempty(UserAgent)\n| summarize StartTime = min(TimeGenerated), EndTime = max(TimeGenerated) by UserAgent, SourceIP = SourceIpAddress, Account = UserIdentityUserName, Type, EventSource, EventName\n))\n// remove wordSize blocks of non-numeric hex characters prior to word extraction\n| extend UserAgentNoHexAlphas = replace(\"([A-Fa-f]{4,})\", \"x\", UserAgent)\n// once blocks of hex chars are removed, extract wordSize blocks of a-z\n| extend Tokens = extract_all(\"([A-Za-z]{4,})\", UserAgentNoHexAlphas)\n// concatenate extracted words to create a summarized user agent for baseline and comparison\n| extend NormalizedUserAgent = strcat_array(Tokens, \"|\")\n| project-away UserAgentNoHexAlphas, Tokens;\nUserAgentAll\n| where StartTime >= ago(endtime)\n| summarize StartTime = min(StartTime), EndTime = max(EndTime), count() by UserAgent, NormalizedUserAgent, SourceIP, Account, Type, RecordType, Operation, EventSource, EventName, sSiteName, csMethod, csUriStem\n| join kind=leftanti\n(\nUserAgentAll\n| where StartTime < ago(endtime)\n| summarize by NormalizedUserAgent, SourceIP, Account, Type, RecordType, Operation, EventSource, EventName, sSiteName, csMethod, csUriStem\n)\non NormalizedUserAgent\n| extend timestamp = StartTime, IPCustomEntity = SourceIP, AccountCustomEntity = Account\n",
        "queryFrequency": "P1D",
        "queryPeriod": "P14D",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0,
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess",
          "CommandAndControl",
          "Execution"
        ],
        "techniques": [
          "T1189",
          "T1071",
          "T1203"
        ],
        "alertRuleTemplateName": "b725d62c-eb77-42ff-96f6-bdc6745fc6e0",
        "customDetails": null,
        "entityMappings": [
          {
            "fieldMappings": [
              {
                "identifier": "FullName",
                "columnName": "AccountCustomEntity"
              }
            ],
            "entityType": "Account"
          },
          {
            "fieldMappings": [
              {
                "identifier": "Address",
                "columnName": "IPCustomEntity"
              }
            ],
            "entityType": "IP"
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Network Threat Protection Essentials/Analytic Rules/NewUserAgentLast24h.yaml",
        "status": "Available",
        "templateVersion": "1.0.2"
      }
    }
  ]
}