Windows Unusual Count Of Users Failed To Authenticate From Process
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
Kill Chain Phase
- Exploitation
NIST
- DE.AE
CIS20
- CIS 10
CVE
Search
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`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:
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
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