Name:GCP Unusual Number of Failed Authentications From Ip id:bd8097ed-958a-4873-87d9-44f2b4d85705 version:3 date:2024-09-30 author:Bhavin Patel, Splunk status:production type:Anomaly Description:The following analytic identifies a single source IP failing to authenticate into Google Workspace with multiple valid users, potentially indicating a Password Spraying attack. It uses Google Workspace login failure events and calculates the standard deviation for source IPs, applying the 3-sigma rule to detect unusual failed authentication attempts. This activity is significant as it may signal an adversary attempting to gain initial access or elevate privileges. If confirmed malicious, this could lead to unauthorized access, data breaches, or further exploitation within the environment. Data_source:
-Google Workspace login_failure
search:`gws_reports_login` event.type = login event.name = login_failure| bucket span=5m _time | stats dc(user_name) AS unique_accounts values(user_name) as tried_accounts values(authentication_method) AS authentication_method by _time, src | eventstats avg(unique_accounts) as ip_avg , stdev(unique_accounts) as ip_std by _time | eval upperBound=(ip_avg+ip_std*3) | eval isOutlier=if(unique_accounts > 10 and unique_accounts >= upperBound, 1, 0) | where isOutlier =1| `gcp_unusual_number_of_failed_authentications_from_ip_filter`
how_to_implement:You must install the latest version of Splunk Add-on for Google Workspace from Splunkbase (https://splunkbase.splunk.com/app/5556) which allows Splunk administrators to collect Google Workspace event data in Splunk using Google Workspace APIs. We would also recommend tuning the detection by adjusting the window `span` and `unique_accounts` threshold values according to your environment. Specifically, this analytic leverages the User log events. known_false_positives:No known false positives for this detection. Please review this alert References: -https://cloud.google.com/blog/products/identity-security/how-google-cloud-can-help-stop-credential-stuffing-attacks -https://www.slideshare.net/dafthack/ok-google-how-do-i-red-team-gsuite -https://attack.mitre.org/techniques/T1110/003/ -https://www.blackhillsinfosec.com/wp-content/uploads/2020/05/Breaching-the-Cloud-Perimeter-Slides.pdf drilldown_searches: name:'View the detection results for - "$tried_accounts$"' search:'%original_detection_search% | search tried_accounts = "$tried_accounts$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$tried_accounts$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$tried_accounts$") starthoursago=168 | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' tags: analytic_story: - 'GCP Account Takeover' asset_type:Google Cloud Platform tenant confidence:90 impact:60 message:Unusual number of failed console login attempts (Count: $unique_accounts$) against users from IP Address - $src$ mitre_attack_id: - 'T1586' - 'T1586.003' - 'T1110' - 'T1110.003' - 'T1110.004' observable: name:'src' type:'IP Address' - role: - 'Attacker' name:'tried_accounts' type:'User' - role: - 'Victim' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'event.name' - 'src' - 'event.type' - 'user_name' risk_score:54 security_domain:threat
