Detect Domain Controller Authentication in Splunk
Adversaries may patch the authentication process on a domain controller to bypass typical authentication mechanisms and enable access to accounts. Malware such as Skeleton Key is injected into LSASS on a domain controller, allowing any user to authenticate with a hardcoded backdoor password. The patch persists only in memory and is erased upon reboot, making detection during active exploitation critical. Chimera group has used this technique to allow login without valid credentials.
MITRE ATT&CK
- Technique
- T1556 Modify Authentication Process
- Sub-technique
- T1556.001 Domain Controller Authentication
- Canonical reference
- https://attack.mitre.org/techniques/T1556/001/
SPL Detection Query
index=wineventlog sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=10
TargetImage="*\\lsass.exe"
NOT (SourceImage="*\\MsMpEng.exe" OR SourceImage="*\\csrss.exe" OR SourceImage="*\\werfault.exe"
OR SourceImage="*\\taskmgr.exe" OR SourceImage="*\\services.exe" OR SourceImage="*\\lsm.exe"
OR SourceImage="*\\svchost.exe" OR SourceImage="*\\winlogon.exe" OR SourceImage="*\\wmiprvse.exe")
| eval HighPrivAccess=if(match(GrantedAccess, "^0x1[f3][0-9a-f]{4}$"), 1, 0)
| eval SkeletonKeyTool=if(match(lower(SourceImage), "(mimikatz|skeleton)"), 1, 0)
| where HighPrivAccess=1 OR SkeletonKeyTool=1
| eval RiskScore=HighPrivAccess + SkeletonKeyTool
| table _time, host, SourceImage, SourceCommandLine, TargetImage, GrantedAccess, SourceUser, RiskScore
| sort - _time
| union
[search index=wineventlog sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=1
(CommandLine="*misc::skeleton*" OR CommandLine="*skeleton key*" OR CommandLine="*SkeletonKey*")
| table _time, host, Image, CommandLine, User]Detects Skeleton Key domain controller backdoor injection using Sysmon Event ID 10 (Process Access) targeting lsass.exe from unexpected source processes with high-privilege access masks, combined with Sysmon Event ID 1 (Process Create) for known Skeleton Key tool command-line patterns. The union combines both detection approaches into a single alert stream.
Data Sources
Required Sourcetypes
False Positives & Tuning
- EDR agents accessing LSASS for memory scanning — build allowlist of known EDR process paths
- WerFault.exe during system crash dump creation — correlate with System Event Log crash events
- Task Manager used by administrators to view LSASS memory on non-DC systems
- Vulnerability scanners performing privilege assessment against LSASS
Other platforms for T1556.001
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Mimikatz Skeleton Key Injection (Simulated — Non-DC)
Expected signal: Sysmon Event ID 1: Process Create with Image=mimikatz.exe, CommandLine containing 'misc::skeleton'. Security Event ID 4688 with ProcessCommandLine=mimikatz.exe. If run with sufficient privilege, Sysmon Event ID 10 will show lsass.exe being accessed with high privilege mask.
- Test 2Suspicious LSASS Access via ProcDump
Expected signal: Sysmon Event ID 10: ProcessAccess with TargetImage=lsass.exe, SourceImage=procdump.exe, GrantedAccess=0x1fffff. Sysmon Event ID 11: FileCreate for the .dmp file. Security Event ID 4688 for procdump.exe process creation.
- Test 3LSASS Access via Task Manager (Low-Fidelity Baseline Test)
Expected signal: Sysmon Event ID 1: Process Create for powershell.exe with Get-Process lsass in CommandLine. PowerShell ScriptBlock Log Event ID 4104 with the script content. Security Event ID 4688 for powershell.exe.
References (7)
- https://attack.mitre.org/techniques/T1556/001/
- https://www.secureworks.com/research/skeleton-key-malware-analysis
- https://technet.microsoft.com/en-us/library/dn487457.aspx
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1556.001/T1556.001.md
- https://blog.gentilkiwi.com/securite/mimikatz/skeleton-key
- https://docs.microsoft.com/en-us/windows/security/identity-protection/credential-guard/credential-guard
- https://medium.com/threatpunter/detecting-attempts-to-steal-passwords-from-memory-558f16dce4ea
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