Windows Unusual Count Of Users Failed To Authenticate From Process

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Description

The following analytic identifies a source process failing to authenticate multiple users, potentially indicating a Password Spraying attack. It leverages Windows Event 4625, which logs failed logon attempts, and uses statistical analysis to detect anomalies. 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, the attacker could compromise multiple accounts, leading to unauthorized access, data exfiltration, or further lateral movement within the network.

• Type: Anomaly

• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

• Last Updated: 2024-05-21
• Author: Mauricio Velazco, Splunk
• ID: 25bdb6cb-2e49-4d34-a93c-d6c567c122fe

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1110.003	Password Spraying	Credential Access

T1110

Brute Force

Credential Access

Kill Chain Phase

• Exploitation

NIST

• DE.AE

CIS20

• CIS 10

CVE

Search

 `wineventlog_security`  EventCode=4625 Logon_Type=2 ProcessName!="-" 
| bucket span=2m _time 
| stats dc(TargetUserName) AS unique_accounts values(TargetUserName) as user by _time, ProcessName, SubjectUserName, Computer 
| eventstats avg(unique_accounts) as comp_avg , stdev(unique_accounts) as comp_std by ProcessName, SubjectUserName, 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_failed_to_authenticate_from_process_filter`

Macros

The SPL above uses the following Macros:

• wineventlog_security

windows_unusual_count_of_users_failed_to_authenticate_from_process_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

• _time
• EventCode
• Logon_Type
• ProcessName
• SubjectUserName
• TargetUserName
• Computer

How To Implement

To successfully implement this search, you need to be ingesting Windows Event Logs from domain controllers aas 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 process failing to authenticate with multiple users is not a common behavior for legitimate user sessions. Possible false positive scenarios include but are not limited to vulnerability scanners and missconfigured systems.

Associated Analytic Story

• Active Directory Password Spraying
• Insider Threat
• Volt Typhoon

RBA

Risk Score	Impact	Confidence	Message
49.0	70	70	Potential password spraying attack from $Computer$

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

• 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

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 2