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The following analytic identifies a source user failing to authenticate with multiple users using explicit credentials on a host. It leverages Windows Event Code 4648 and calculates the standard deviation for each host, using the 3-sigma rule to detect anomalies. This behavior is significant as it may indicate a Password Spraying attack, where an adversary attempts to gain initial access or elevate privileges. If confirmed malicious, this activity could lead to unauthorized access, privilege escalation, or further compromise of the Active Directory environment.

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

  • Last Updated: 2024-05-14
  • Author: Mauricio Velazco, Splunk
  • ID: 14f414cf-3080-4b9b-aaf6-55a4ce947b93




ID Technique Tactic
T1110.003 Password Spraying Credential Access
T1110 Brute Force Credential Access
Kill Chain Phase
  • Exploitation
  • DE.AE
  • CIS 10
 `wineventlog_security` EventCode=4648 Caller_User_Name!=*$ Target_User_Name!=*$ 
| bucket span=5m _time 
| stats dc(Target_User_Name) AS unique_accounts values(Target_User_Name) as  user by _time, Computer, Caller_User_Name 
| eventstats avg(unique_accounts) as comp_avg , stdev(unique_accounts) as comp_std by 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_fail_to_auth_wth_explicitcredentials_filter`


The SPL above uses the following Macros:

:information_source: windows_unusual_count_of_users_fail_to_auth_wth_explicitcredentials_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
  • Target_User_Name
  • Caller_User_Name
  • Computer

How To Implement

To successfully implement this search, you need to be ingesting Windows Event Logs from domain controllers 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 source user failing attempting to authenticate multiple users on a host is not a common behavior for regular systems. Some applications, however, may exhibit this behavior in which case sets of users hosts can be added to an allow list. Possible false positive scenarios include systems where several users connect to like Mail servers, identity providers, remote desktop services, Citrix, etc.

Associated Analytic Story


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

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


Test Dataset

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

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