GCP Excessive Permission Denied Events

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 * Copyright 2024 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 gcp_excessive_permission_denied_events {

  meta:
    author = "Google Cloud Security"
    description = "Detects excessive PermissionDenied events within an hour timeframe from a user"
    rule_id = "mr_2edbd86a-703a-41a3-b2b2-596dd9dbed8d"
    rule_name = "GCP Excessive Permission Denied Events"
    mitre_attack_tactic = "Discovery"
    mitre_attack_technique = "Cloud Infrastructure Discovery"
    mitre_attack_url = "https://attack.mitre.org/techniques/T1580/"
    mitre_attack_version = "v14.1"
    type = "Alert"
    data_source = "GCP Cloud Audit"
    platform = "GCP"
    severity = "Low"
    priority = "Low"

 events:
    $gcp.metadata.log_type = "GCP_CLOUDAUDIT"
    $gcp.security_result.action = "BLOCK"
    $gcp.security_result.severity = "ERROR"
    $gcp.security_result.detection_fields["status_code"] = "7"
    $gcp.principal.user.userid = $user_id
    $gcp.target.application = $target_application
    $gcp.metadata.product_event_type = $product_event_type

  match:
    $user_id over 1h

  outcome:
    $risk_score = max(35)
    $mitre_attack_tactic = "Discovery"
    $mitre_attack_technique = "Cloud Infrastructure Discovery"
    $mitre_attack_technique_id = "T1580"
    $event_count = count_distinct($gcp.metadata.id)
    $network_http_user_agent = array_distinct($gcp.network.http.user_agent)
    $principal_ip = array_distinct($gcp.principal.ip)
    $principal_ip_country = array_distinct($gcp.principal.ip_geo_artifact.location.country_or_region)
    $principal_ip_state = array_distinct($gcp.principal.ip_geo_artifact.location.state)
    $principal_user_display_name = array_distinct($gcp.principal.user.user_display_name)
    $target_resource_name = array_distinct($gcp.target.resource.name)

  condition:
    #gcp > 5 and #target_application > 1 and #product_event_type > 1
}