Windows Unusual Count Of Users Remotely Failed To Auth From Host
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.
- Type: Anomaly
-
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2024-05-18
- Author: Mauricio Velazco, Splunk
- ID: cf06a0ee-ffa9-4ed3-be77-0670ed9bab52
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=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`
Macros
The SPL above uses the following Macros:
windows_unusual_count_of_users_remotely_failed_to_auth_from_host_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
- TargetUserName
- Computer
- IpAddress
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.
Associated Analytic Story
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
49.0 | 70 | 70 | Potential password spraying attack on $Computer$ |
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