GSA Enriched Office 365 - New Windows Reserved Filenames staged on Office file services

let starttime = todatetime('{{StartTimeISO}}');
  let endtime = todatetime('{{EndTimeISO}}');
  let lookback = totimespan((endtime - starttime) * 7);
  
  // Reserved file names and extensions for Windows
  let Reserved = dynamic(['CON', 'PRN', 'AUX', 'NUL', 'COM1', 'COM2', 'COM3', 'COM4', 'COM5', 'COM6', 'COM7', 'COM8', 'COM9', 'LPT1', 'LPT2', 'LPT3', 'LPT4', 'LPT5', 'LPT6', 'LPT7', 'LPT8', 'LPT9']);
  
  // EnrichedMicrosoft365AuditLogs Query
  let EnrichedEvents = EnrichedMicrosoft365AuditLogs
      | where TimeGenerated between (starttime .. endtime)
      | extend FileName = tostring(parse_json(tostring(AdditionalProperties)).SourceFileName)
      | extend ClientUserAgent = tostring(parse_json(tostring(AdditionalProperties)).ClientUserAgent)
      | extend SiteUrl = tostring(parse_json(tostring(AdditionalProperties)).SiteUrl)
      | where isnotempty(ObjectId)
      | where ObjectId !~ FileName
      | where ObjectId in (Reserved) or FileName in (Reserved)
      | where ClientUserAgent !has "Mac OS"
      | join kind=leftanti (
          EnrichedMicrosoft365AuditLogs
          | where TimeGenerated between (ago(lookback) .. starttime)
          | extend FileName = tostring(parse_json(tostring(AdditionalProperties)).SourceFileName)
          | extend ClientUserAgent = tostring(parse_json(tostring(AdditionalProperties)).ClientUserAgent)
          | extend SiteUrl = tostring(parse_json(tostring(AdditionalProperties)).SiteUrl)
          | where isnotempty(ObjectId)
          | where ObjectId !~ FileName
          | where ObjectId in (Reserved) or FileName in (Reserved)
          | where ClientUserAgent !has "Mac OS"
          | summarize PrevSeenCount = count() by ObjectId, UserId, FileName
      ) on ObjectId
      | extend SiteUrlUserFolder = tolower(split(SiteUrl, '/')[-2])
      | extend UserIdUserFolderFormat = tolower(replace_regex(UserId, '@|\\.', '_'))
      | extend UserIdDiffThanUserFolder = iff(SiteUrl has '/personal/' and SiteUrlUserFolder != UserIdUserFolderFormat, true, false)
      | summarize TimeGenerated = make_list(TimeGenerated, 100000), StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), Operations = make_list(Operation, 100000), UserAgents = make_list(ClientUserAgent, 100000), Ids = make_list(Id, 100000),
          SourceRelativeUrls = make_list(ObjectId, 100000), FileNames = make_list(FileName, 100000) by Workload, RecordType, UserType, UserKey, UserId, ClientIp, SiteUrl, ObjectId, SiteUrlUserFolder, UserIdUserFolderFormat, UserIdDiffThanUserFolder
      | extend AccountName = tostring(split(UserId, "@")[0]), AccountUPNSuffix = tostring(split(UserId, "@")[1])
      | extend IP_0_Address = ClientIp
      | extend Account_0_Name = AccountName, Account_0_UPNSuffix = AccountUPNSuffix, URL_0_Url = SiteUrl;
  // OfficeActivity Query
  let OfficeEvents = OfficeActivity
      | where TimeGenerated between (starttime .. endtime)
      | where isnotempty(SourceFileExtension)
      | where SourceFileName !~ SourceFileExtension
      | where SourceFileExtension in (Reserved) or SourceFileName in (Reserved)
      | where UserAgent !has "Mac OS"
      | join kind=leftanti (
          OfficeActivity
          | where TimeGenerated between (ago(lookback) .. starttime)
          | where isnotempty(SourceFileExtension)
          | where SourceFileName !~ SourceFileExtension
          | where SourceFileExtension in (Reserved) or SourceFileName in (Reserved)
          | where UserAgent !has "Mac OS"
          | summarize PrevSeenCount = count() by SourceFileExtension
      ) on SourceFileExtension
      | extend SiteUrlUserFolder = tolower(split(Site_Url, '/')[-2])
      | extend UserIdUserFolderFormat = tolower(replace_regex(UserId, '@|\\.', '_'))
      | extend UserIdDiffThanUserFolder = iff(Site_Url has '/personal/' and SiteUrlUserFolder != UserIdUserFolderFormat, true, false)
      | summarize TimeGenerated = make_list(TimeGenerated, 100000), StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), Operations = make_list(Operation, 100000), UserAgents = make_list(UserAgent, 100000), OfficeIds = make_list(OfficeId, 100000),
          SourceRelativeUrls = make_list(SourceRelativeUrl, 100000), FileNames = make_list(SourceFileName, 100000) by OfficeWorkload, RecordType, UserType, UserKey, UserId, ClientIP, Site_Url, SourceFileExtension, SiteUrlUserFolder, UserIdUserFolderFormat, UserIdDiffThanUserFolder
      | extend AccountName = tostring(split(UserId, "@")[0]), AccountUPNSuffix = tostring(split(UserId, "@")[1])
      | extend IP_0_Address = ClientIP
      | extend Account_0_Name = AccountName, Account_0_UPNSuffix = AccountUPNSuffix, URL_0_Url = Site_Url;
  // Combine Office and Enriched Logs
  let CombinedEvents = OfficeEvents
      | union EnrichedEvents
      | summarize arg_min(StartTime, *) by UserId, ClientIP;
  // Final Output
  CombinedEvents
      | project StartTime, EndTime, Operations, UserAgents, IP_0_Address, Account_0_Name, Account_0_UPNSuffix, URL_0_Url
      | order by StartTime desc

relevantTechniques:
- T1105
name: GSA Enriched Office 365 - New Windows Reserved Filenames staged on Office file services
requiredDataConnectors:
- dataTypes:
  - EnrichedMicrosoft365AuditLogs
  connectorId: AzureActiveDirectory
entityMappings:
- fieldMappings:
  - identifier: Address
    columnName: IP_0_Address
  entityType: IP
- fieldMappings:
  - identifier: Name
    columnName: AccountName
  - identifier: UPNSuffix
    columnName: AccountUPNSuffix
  entityType: Account
- fieldMappings:
  - identifier: Url
    columnName: URL_0_Url
  entityType: URL
query: "let starttime = todatetime('{{StartTimeISO}}');\n  let endtime = todatetime('{{EndTimeISO}}');\n  let lookback = totimespan((endtime - starttime) * 7);\n  \n  // Reserved file names and extensions for Windows\n  let Reserved = dynamic(['CON', 'PRN', 'AUX', 'NUL', 'COM1', 'COM2', 'COM3', 'COM4', 'COM5', 'COM6', 'COM7', 'COM8', 'COM9', 'LPT1', 'LPT2', 'LPT3', 'LPT4', 'LPT5', 'LPT6', 'LPT7', 'LPT8', 'LPT9']);\n  \n  // EnrichedMicrosoft365AuditLogs Query\n  let EnrichedEvents = EnrichedMicrosoft365AuditLogs\n      | where TimeGenerated between (starttime .. endtime)\n      | extend FileName = tostring(parse_json(tostring(AdditionalProperties)).SourceFileName)\n      | extend ClientUserAgent = tostring(parse_json(tostring(AdditionalProperties)).ClientUserAgent)\n      | extend SiteUrl = tostring(parse_json(tostring(AdditionalProperties)).SiteUrl)\n      | where isnotempty(ObjectId)\n      | where ObjectId !~ FileName\n      | where ObjectId in (Reserved) or FileName in (Reserved)\n      | where ClientUserAgent !has \"Mac OS\"\n      | join kind=leftanti (\n          EnrichedMicrosoft365AuditLogs\n          | where TimeGenerated between (ago(lookback) .. starttime)\n          | extend FileName = tostring(parse_json(tostring(AdditionalProperties)).SourceFileName)\n          | extend ClientUserAgent = tostring(parse_json(tostring(AdditionalProperties)).ClientUserAgent)\n          | extend SiteUrl = tostring(parse_json(tostring(AdditionalProperties)).SiteUrl)\n          | where isnotempty(ObjectId)\n          | where ObjectId !~ FileName\n          | where ObjectId in (Reserved) or FileName in (Reserved)\n          | where ClientUserAgent !has \"Mac OS\"\n          | summarize PrevSeenCount = count() by ObjectId, UserId, FileName\n      ) on ObjectId\n      | extend SiteUrlUserFolder = tolower(split(SiteUrl, '/')[-2])\n      | extend UserIdUserFolderFormat = tolower(replace_regex(UserId, '@|\\\\.', '_'))\n      | extend UserIdDiffThanUserFolder = iff(SiteUrl has '/personal/' and SiteUrlUserFolder != UserIdUserFolderFormat, true, false)\n      | summarize TimeGenerated = make_list(TimeGenerated, 100000), StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), Operations = make_list(Operation, 100000), UserAgents = make_list(ClientUserAgent, 100000), Ids = make_list(Id, 100000),\n          SourceRelativeUrls = make_list(ObjectId, 100000), FileNames = make_list(FileName, 100000) by Workload, RecordType, UserType, UserKey, UserId, ClientIp, SiteUrl, ObjectId, SiteUrlUserFolder, UserIdUserFolderFormat, UserIdDiffThanUserFolder\n      | extend AccountName = tostring(split(UserId, \"@\")[0]), AccountUPNSuffix = tostring(split(UserId, \"@\")[1])\n      | extend IP_0_Address = ClientIp\n      | extend Account_0_Name = AccountName, Account_0_UPNSuffix = AccountUPNSuffix, URL_0_Url = SiteUrl;\n  // OfficeActivity Query\n  let OfficeEvents = OfficeActivity\n      | where TimeGenerated between (starttime .. endtime)\n      | where isnotempty(SourceFileExtension)\n      | where SourceFileName !~ SourceFileExtension\n      | where SourceFileExtension in (Reserved) or SourceFileName in (Reserved)\n      | where UserAgent !has \"Mac OS\"\n      | join kind=leftanti (\n          OfficeActivity\n          | where TimeGenerated between (ago(lookback) .. starttime)\n          | where isnotempty(SourceFileExtension)\n          | where SourceFileName !~ SourceFileExtension\n          | where SourceFileExtension in (Reserved) or SourceFileName in (Reserved)\n          | where UserAgent !has \"Mac OS\"\n          | summarize PrevSeenCount = count() by SourceFileExtension\n      ) on SourceFileExtension\n      | extend SiteUrlUserFolder = tolower(split(Site_Url, '/')[-2])\n      | extend UserIdUserFolderFormat = tolower(replace_regex(UserId, '@|\\\\.', '_'))\n      | extend UserIdDiffThanUserFolder = iff(Site_Url has '/personal/' and SiteUrlUserFolder != UserIdUserFolderFormat, true, false)\n      | summarize TimeGenerated = make_list(TimeGenerated, 100000), StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), Operations = make_list(Operation, 100000), UserAgents = make_list(UserAgent, 100000), OfficeIds = make_list(OfficeId, 100000),\n          SourceRelativeUrls = make_list(SourceRelativeUrl, 100000), FileNames = make_list(SourceFileName, 100000) by OfficeWorkload, RecordType, UserType, UserKey, UserId, ClientIP, Site_Url, SourceFileExtension, SiteUrlUserFolder, UserIdUserFolderFormat, UserIdDiffThanUserFolder\n      | extend AccountName = tostring(split(UserId, \"@\")[0]), AccountUPNSuffix = tostring(split(UserId, \"@\")[1])\n      | extend IP_0_Address = ClientIP\n      | extend Account_0_Name = AccountName, Account_0_UPNSuffix = AccountUPNSuffix, URL_0_Url = Site_Url;\n  // Combine Office and Enriched Logs\n  let CombinedEvents = OfficeEvents\n      | union EnrichedEvents\n      | summarize arg_min(StartTime, *) by UserId, ClientIP;\n  // Final Output\n  CombinedEvents\n      | project StartTime, EndTime, Operations, UserAgents, IP_0_Address, Account_0_Name, Account_0_UPNSuffix, URL_0_Url\n      | order by StartTime desc\n"
id: 641ecd2d-27c9-4f05-8433-8205096b09fc
tactics:
- CommandAndControl
version: 2.0.2
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Global Secure Access/Hunting Queries/New_WindowsReservedFileNamesOnOfficeFileServices.yaml
kind: Scheduled
description-detailed: |
  'Identifies when new Windows Reserved Filenames show up on Office services such as SharePoint and OneDrive in relation to the previous 7 days.
  List currently includes ''CON'', ''PRN'', ''AUX'', ''NUL'', ''COM1'', ''COM2'', ''COM3'', ''COM4'', ''COM5'', ''COM6'',
  ''COM7'', ''COM8'', ''COM9'', ''LPT1'', ''LPT2'', ''LPT3'', ''LPT4'', ''LPT5'', ''LPT6'', ''LPT7'', ''LPT8'', ''LPT9'' file extensions.
  Additionally, identifies when a given user is uploading these files to another users workspace.
  This may be indication of a staging location for malware or other malicious activity.
  References: https://docs.microsoft.com/windows/win32/fileio/naming-a-file'  
description: |
    'This identifies new Windows Reserved Filenames on Office services like SharePoint and OneDrive in the past 7 days. It also detects when a user uploads these files to another user's workspace, which may indicate malicious activity.'

{
  "$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/641ecd2d-27c9-4f05-8433-8205096b09fc')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/641ecd2d-27c9-4f05-8433-8205096b09fc')]",
      "properties": {
        "alertRuleTemplateName": "641ecd2d-27c9-4f05-8433-8205096b09fc",
        "customDetails": null,
        "description": "'This identifies new Windows Reserved Filenames on Office services like SharePoint and OneDrive in the past 7 days. It also detects when a user uploads these files to another user's workspace, which may indicate malicious activity.'\n",
        "description-detailed": "'Identifies when new Windows Reserved Filenames show up on Office services such as SharePoint and OneDrive in relation to the previous 7 days.\nList currently includes ''CON'', ''PRN'', ''AUX'', ''NUL'', ''COM1'', ''COM2'', ''COM3'', ''COM4'', ''COM5'', ''COM6'',\n''COM7'', ''COM8'', ''COM9'', ''LPT1'', ''LPT2'', ''LPT3'', ''LPT4'', ''LPT5'', ''LPT6'', ''LPT7'', ''LPT8'', ''LPT9'' file extensions.\nAdditionally, identifies when a given user is uploading these files to another users workspace.\nThis may be indication of a staging location for malware or other malicious activity.\nReferences: https://docs.microsoft.com/windows/win32/fileio/naming-a-file'\n",
        "displayName": "GSA Enriched Office 365 - New Windows Reserved Filenames staged on Office file services",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "IP_0_Address",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "Account",
            "fieldMappings": [
              {
                "columnName": "AccountName",
                "identifier": "Name"
              },
              {
                "columnName": "AccountUPNSuffix",
                "identifier": "UPNSuffix"
              }
            ]
          },
          {
            "entityType": "URL",
            "fieldMappings": [
              {
                "columnName": "URL_0_Url",
                "identifier": "Url"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Global Secure Access/Hunting Queries/New_WindowsReservedFileNamesOnOfficeFileServices.yaml",
        "query": "let starttime = todatetime('{{StartTimeISO}}');\n  let endtime = todatetime('{{EndTimeISO}}');\n  let lookback = totimespan((endtime - starttime) * 7);\n  \n  // Reserved file names and extensions for Windows\n  let Reserved = dynamic(['CON', 'PRN', 'AUX', 'NUL', 'COM1', 'COM2', 'COM3', 'COM4', 'COM5', 'COM6', 'COM7', 'COM8', 'COM9', 'LPT1', 'LPT2', 'LPT3', 'LPT4', 'LPT5', 'LPT6', 'LPT7', 'LPT8', 'LPT9']);\n  \n  // EnrichedMicrosoft365AuditLogs Query\n  let EnrichedEvents = EnrichedMicrosoft365AuditLogs\n      | where TimeGenerated between (starttime .. endtime)\n      | extend FileName = tostring(parse_json(tostring(AdditionalProperties)).SourceFileName)\n      | extend ClientUserAgent = tostring(parse_json(tostring(AdditionalProperties)).ClientUserAgent)\n      | extend SiteUrl = tostring(parse_json(tostring(AdditionalProperties)).SiteUrl)\n      | where isnotempty(ObjectId)\n      | where ObjectId !~ FileName\n      | where ObjectId in (Reserved) or FileName in (Reserved)\n      | where ClientUserAgent !has \"Mac OS\"\n      | join kind=leftanti (\n          EnrichedMicrosoft365AuditLogs\n          | where TimeGenerated between (ago(lookback) .. starttime)\n          | extend FileName = tostring(parse_json(tostring(AdditionalProperties)).SourceFileName)\n          | extend ClientUserAgent = tostring(parse_json(tostring(AdditionalProperties)).ClientUserAgent)\n          | extend SiteUrl = tostring(parse_json(tostring(AdditionalProperties)).SiteUrl)\n          | where isnotempty(ObjectId)\n          | where ObjectId !~ FileName\n          | where ObjectId in (Reserved) or FileName in (Reserved)\n          | where ClientUserAgent !has \"Mac OS\"\n          | summarize PrevSeenCount = count() by ObjectId, UserId, FileName\n      ) on ObjectId\n      | extend SiteUrlUserFolder = tolower(split(SiteUrl, '/')[-2])\n      | extend UserIdUserFolderFormat = tolower(replace_regex(UserId, '@|\\\\.', '_'))\n      | extend UserIdDiffThanUserFolder = iff(SiteUrl has '/personal/' and SiteUrlUserFolder != UserIdUserFolderFormat, true, false)\n      | summarize TimeGenerated = make_list(TimeGenerated, 100000), StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), Operations = make_list(Operation, 100000), UserAgents = make_list(ClientUserAgent, 100000), Ids = make_list(Id, 100000),\n          SourceRelativeUrls = make_list(ObjectId, 100000), FileNames = make_list(FileName, 100000) by Workload, RecordType, UserType, UserKey, UserId, ClientIp, SiteUrl, ObjectId, SiteUrlUserFolder, UserIdUserFolderFormat, UserIdDiffThanUserFolder\n      | extend AccountName = tostring(split(UserId, \"@\")[0]), AccountUPNSuffix = tostring(split(UserId, \"@\")[1])\n      | extend IP_0_Address = ClientIp\n      | extend Account_0_Name = AccountName, Account_0_UPNSuffix = AccountUPNSuffix, URL_0_Url = SiteUrl;\n  // OfficeActivity Query\n  let OfficeEvents = OfficeActivity\n      | where TimeGenerated between (starttime .. endtime)\n      | where isnotempty(SourceFileExtension)\n      | where SourceFileName !~ SourceFileExtension\n      | where SourceFileExtension in (Reserved) or SourceFileName in (Reserved)\n      | where UserAgent !has \"Mac OS\"\n      | join kind=leftanti (\n          OfficeActivity\n          | where TimeGenerated between (ago(lookback) .. starttime)\n          | where isnotempty(SourceFileExtension)\n          | where SourceFileName !~ SourceFileExtension\n          | where SourceFileExtension in (Reserved) or SourceFileName in (Reserved)\n          | where UserAgent !has \"Mac OS\"\n          | summarize PrevSeenCount = count() by SourceFileExtension\n      ) on SourceFileExtension\n      | extend SiteUrlUserFolder = tolower(split(Site_Url, '/')[-2])\n      | extend UserIdUserFolderFormat = tolower(replace_regex(UserId, '@|\\\\.', '_'))\n      | extend UserIdDiffThanUserFolder = iff(Site_Url has '/personal/' and SiteUrlUserFolder != UserIdUserFolderFormat, true, false)\n      | summarize TimeGenerated = make_list(TimeGenerated, 100000), StartTime = min(TimeGenerated), EndTime = max(TimeGenerated), Operations = make_list(Operation, 100000), UserAgents = make_list(UserAgent, 100000), OfficeIds = make_list(OfficeId, 100000),\n          SourceRelativeUrls = make_list(SourceRelativeUrl, 100000), FileNames = make_list(SourceFileName, 100000) by OfficeWorkload, RecordType, UserType, UserKey, UserId, ClientIP, Site_Url, SourceFileExtension, SiteUrlUserFolder, UserIdUserFolderFormat, UserIdDiffThanUserFolder\n      | extend AccountName = tostring(split(UserId, \"@\")[0]), AccountUPNSuffix = tostring(split(UserId, \"@\")[1])\n      | extend IP_0_Address = ClientIP\n      | extend Account_0_Name = AccountName, Account_0_UPNSuffix = AccountUPNSuffix, URL_0_Url = Site_Url;\n  // Combine Office and Enriched Logs\n  let CombinedEvents = OfficeEvents\n      | union EnrichedEvents\n      | summarize arg_min(StartTime, *) by UserId, ClientIP;\n  // Final Output\n  CombinedEvents\n      | project StartTime, EndTime, Operations, UserAgents, IP_0_Address, Account_0_Name, Account_0_UPNSuffix, URL_0_Url\n      | order by StartTime desc\n",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "CommandAndControl"
        ],
        "techniques": [
          "T1105"
        ],
        "templateVersion": "2.0.2"
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}