Name:Windows Unusual Count Of Users Remotely Failed To Auth From Host id:cf06a0ee-ffa9-4ed3-be77-0670ed9bab52 version:4 date:2024-09-30 author:Mauricio Velazco, Splunk status:production type:Anomaly Description:The following analytic identifies a source host failing to authenticate against a remote host with multiple users, potentially indicating a Password Spraying attack. It leverages Windows Event 4625 (failed logon attempts) and Logon Type 3 (remote authentication) to detect this behavior. This activity is significant as it may represent an adversary attempting to gain initial access or elevate privileges within an Active Directory environment. If confirmed malicious, this could lead to unauthorized access, privilege escalation, and further compromise of the network. Data_source:
-Windows Event Log Security 4625
search:`wineventlog_security` EventCode=4625 Logon_Type=3 IpAddress!="-" | bucket span=2m _time | stats dc(TargetUserName) AS unique_accounts values(TargetUserName) as tried_accounts by _time, IpAddress, Computer | eventstats avg(unique_accounts) as comp_avg , stdev(unique_accounts) as comp_std by IpAddress, Computer | eval upperBound=(comp_avg+comp_std*3) | eval isOutlier=if(unique_accounts > 10 and unique_accounts >= upperBound, 1, 0) | search isOutlier=1 | `windows_unusual_count_of_users_remotely_failed_to_auth_from_host_filter`
how_to_implement:To successfully implement this search, you need to be ingesting Windows Event Logs from domain controllers as as well as member servers and workstations. The Advanced Security Audit policy setting `Audit Logon` within `Logon/Logoff` needs to be enabled. known_false_positives:A host failing to authenticate with multiple valid users against a remote host is not a common behavior for legitimate systems. Possible false positive scenarios include but are not limited to vulnerability scanners, remote administration tools, missconfigyred systems, etc. References: -https://attack.mitre.org/techniques/T1110/003/ -https://docs.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4625 -https://www.ultimatewindowssecurity.com/securitylog/encyclopedia/event.aspx?eventID=4625 -https://docs.microsoft.com/en-us/windows/security/threat-protection/auditing/basic-audit-logon-events drilldown_searches: name:'View the detection results for - "$Computer$"' search:'%original_detection_search% | search Computer = "$Computer$"' earliest_offset:'$info_min_time$' latest_offset:'$info_max_time$' name:'View risk events for the last 7 days for - "$Computer$"' search:'| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$Computer$") 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: - 'Active Directory Password Spraying' - 'Volt Typhoon' asset_type:Endpoint confidence:70 impact:70 message:Potential password spraying attack on $Computer$ mitre_attack_id: - 'T1110.003' - 'T1110' observable: name:'Computer' - role: - 'Victim' type:'Endpoint' product: - 'Splunk Enterprise' - 'Splunk Enterprise Security' - 'Splunk Cloud' required_fields: - '_time' - 'EventCode' - 'Logon_Type' - 'TargetUserName' - 'Computer' - 'IpAddress' risk_score:49 security_domain:endpoint
