Windows Multiple Invalid Users Failed To Authenticate Using NTLM
Description
The following analytic detects a single source endpoint failing to authenticate with 30 unique invalid users using the NTLM protocol. It leverages EventCode 4776 from Domain Controller logs, focusing on error code 0xC0000064, which indicates non-existent usernames. 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, and potential compromise of sensitive information within the Active Directory environment.
- Type: TTP
-
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2024-05-17
- Author: Mauricio Velazco, Splunk
- ID: 57ad5a64-9df7-11eb-a290-acde48001122
Annotations
ATT&CK
Kill Chain Phase
- Exploitation
NIST
- DE.CM
CIS20
- CIS 10
CVE
Search
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`wineventlog_security` EventCode=4776 TargetUserName!=*$ Status=0xc0000064
| bucket span=5m _time
| stats dc(TargetUserName) AS unique_accounts values(TargetUserName) as tried_accounts by _time, Workstation
| where unique_accounts > 30
| `windows_multiple_invalid_users_failed_to_authenticate_using_ntlm_filter`
Macros
The SPL above uses the following Macros:
windows_multiple_invalid_users_failed_to_authenticate_using_ntlm_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
- TargetUserName
- Workstation
- Status
How To Implement
To successfully implement this search, you need to be ingesting Domain Controller events. The Advanced Security Audit policy setting Audit Credential Validation' within
Account Logon` needs to be enabled.
Known False Positives
A host failing to authenticate with multiple invalid domain users is not a common behavior for legitimate systems. Possible false positive scenarios include but are not limited to vulnerability scanners and missconfigured systems. If this detection triggers on a host other than a Domain Controller, the behavior could represent a password spraying attack against the host's local accounts.
Associated Analytic Story
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
49.0 | 70 | 70 | Potential NTLM based password spraying attack from $Workstation$ |
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/audit-credential-validation
- https://docs.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4776
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: 3