Google Workspace Multiple Files Downloaded From Google Drive

/*
 * Copyright 2023 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

rule google_workspace_multiple_files_downloaded_from_google_drive {

    meta:
      author = "Google Cloud Security"
      description = "Identifies when a user downloads multiple files from Google Drive, which may indicate data exfiltration."
      rule_id = "mr_72855af9-fba4-4424-b879-4de733374e8b"
      rule_name = "Google Workspace Multiple Files Downloaded From Google Drive"
      mitre_attack_tactic = "Exfiltration"
      mitre_attack_technique = "Exfiltration Over Web Service"
      mitre_attack_url = "https://attack.mitre.org/techniques/T1567/"
      mitre_attack_version = "v13.1"
      type = "Alert"
      data_source = "Workspace Activity"
      severity = "High"
      priority = "High"

    events:
      // Document downloaded from Google Drive
      $download.metadata.vendor_name = "Google Workspace"
      $download.metadata.product_name = "drive"
      $download.metadata.product_event_type = "download"
      $download.principal.user.userid = $user_id

    match:
      $user_id over 1h

    outcome:
      $risk_score = max(75)
      $mitre_attack_tactic = "Exfiltration"
      $mitre_attack_technique = "Exfiltration Over Web Service"
      $mitre_attack_technique_id = "T1567"
      $event_count = count_distinct($download.metadata.id)
      $product_event_type = array_distinct($download.metadata.product_event_type)
      $userid = array_distinct($download.principal.user.userid)
      $doc_type = array_distinct($download.src.resource.attribute.labels["doc_type"])
      $owner = array_distinct($download.target.resource.attribute.labels["owner"])
      $doc_name = array_distinct($download.target.resource.name)
      $doc_id = array_distinct($download.target.resource.product_object_id)
      $count_docs = count_distinct($download.target.resource.product_object_id)

    condition:
      // Customize the value of $count_docs to set the alerting threshold for your environment
      $download and $count_docs > 10
  }