name: Detect GCP Storage access from a new IP
id: ccc3246a-daa1-11ea-87d0-0242ac130022
version: 1
date: '2020-08-10'
author: Shannon Davis, Splunk
type: batch
datamodel: []
description: This search looks at GCP Storage bucket-access logs and detects new or
  previously unseen remote IP addresses that have successfully accessed a GCP Storage
  bucket.
search: '`google_gcp_pubsub_message` | multikv | rename sc_status_ as status | rename
  cs_object_ as bucket_name | rename c_ip_ as remote_ip | rename cs_uri_ as request_uri
  | rename cs_method_ as operation | search status="\"200\"" | stats earliest(_time)
  as firstTime latest(_time) as lastTime by bucket_name remote_ip operation request_uri
  | table firstTime, lastTime, bucket_name, remote_ip, operation, request_uri | inputlookup
  append=t previously_seen_gcp_storage_access_from_remote_ip.csv | stats min(firstTime)
  as firstTime, max(lastTime) as lastTime by bucket_name remote_ip operation request_uri
  | outputlookup previously_seen_gcp_storage_access_from_remote_ip.csv | eval newIP=if(firstTime
  >= relative_time(now(),"-70m@m"), 1, 0) | where newIP=1 | eval first_time=strftime(firstTime,"%m/%d/%y
  %H:%M:%S") | eval last_time=strftime(lastTime,"%m/%d/%y %H:%M:%S") | table  first_time
  last_time bucket_name remote_ip operation request_uri | `detect_gcp_storage_access_from_a_new_ip_filter`'
how_to_implement: This search relies on the Splunk Add-on for Google Cloud Platform,
  setting up a Cloud Pub/Sub input, along with the relevant GCP PubSub topics and
  logging sink to capture GCP Storage Bucket events (https://cloud.google.com/logging/docs/routing/overview).
  In order to capture public GCP Storage Bucket access logs, you must also enable
  storage bucket logging to your PubSub Topic as per https://cloud.google.com/storage/docs/access-logs.  These
  logs are deposited into the nominated Storage Bucket on an hourly basis and typically
  show up by 15 minutes past the hour.  It is recommended to configure any saved searches
  or correlation searches in Enterprise Security to run on an hourly basis at 30 minutes
  past the hour (cron definition of 30 * * * *).  A lookup table (previously_seen_gcp_storage_access_from_remote_ip.csv)
  stores the previously seen access requests, and is used by this search to determine
  any newly seen IP addresses accessing the Storage Buckets.
known_false_positives: GCP Storage buckets can be accessed from any IP (if the ACLs
  are open to allow it), as long as it can make a successful connection. This will
  be a false postive, since the search is looking for a new IP within the past two
  hours.
references: []
tags:
  analytic_story:
  - Suspicious GCP Storage Activities
  asset_type: GCP Storage Bucket
  cis20:
  - CIS 13
  - CIS 14
  kill_chain_phases:
  - Actions on Objectives
  mitre_attack_id:
  - T1530
  nist:
  - PR.DS
  - PR.AC
  - DE.CM
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - sc_status_
  - cs_object_
  - c_ip_
  - cs_uri_
  - cs_method_
  security_domain: network
