ID | Technique | Tactic |
---|---|---|
T1110.003 | Password Spraying | Credential Access |
T1110 | Brute Force | Credential Access |
Detection: Windows Unusual Count Of Disabled Users Failed Auth Using Kerberos
Description
The following analytic identifies a source endpoint failing to authenticate with multiple disabled domain users using the Kerberos protocol. It leverages EventCode 4768, which is generated when the Key Distribution Center issues a Kerberos Ticket Granting Ticket (TGT) and detects failure code 0x12
(credentials revoked). This behavior is significant as it may indicate a Password Spraying attack targeting disabled accounts, potentially leading to initial access or privilege escalation. If confirmed malicious, attackers could gain unauthorized access or elevate privileges within the Active Directory environment.
Search
1`wineventlog_security` EventCode=4768 TargetUserName!=*$ Status=0x12
2| bucket span=5m _time
3| stats dc(TargetUserName) AS unique_accounts values(TargetUserName) as user by _time, IpAddress
4| eventstats avg(unique_accounts) as comp_avg , stdev(unique_accounts) as comp_std by IpAddress
5| eval upperBound=(comp_avg+comp_std*3)
6| eval isOutlier=if(unique_accounts > 10 and unique_accounts >= upperBound, 1, 0)
7| search isOutlier=1
8| `windows_unusual_count_of_disabled_users_failed_auth_using_kerberos_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
Windows Event Log Security 4768 | Windows | 'xmlwineventlog' |
'XmlWinEventLog:Security' |
N/A |
Macros Used
Name | Value |
---|---|
wineventlog_security | eventtype=wineventlog_security OR Channel=security OR source=XmlWinEventLog:Security |
windows_unusual_count_of_disabled_users_failed_auth_using_kerberos_filter | search * |
windows_unusual_count_of_disabled_users_failed_auth_using_kerberos_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Risk Event | True |
Implementation
To successfully implement this search, you need to be ingesting Domain Controller and Kerberos events. The Advanced Security Audit policy setting Audit Kerberos Authentication Service
within Account Logon
needs to be enabled.
Known False Positives
A host failing to authenticate with multiple disabled domain users is not a common behavior for legitimate systems. Possible false positive scenarios include but are not limited to vulnerability scanners, multi-user systems missconfigured systems.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
Potential Kerberos based password spraying attack from $IpAddress$ | 49 | 70 | 70 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | XmlWinEventLog:Security |
XmlWinEventLog |
Integration | ✅ Passing | Dataset | XmlWinEventLog:Security |
XmlWinEventLog |
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: GitHub | Version: 2