Detect Domain Controller Authentication in Microsoft Sentinel
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/
KQL Detection Query
let SkeletonKeyIndicators = dynamic([
"SkeletonKey", "skeleton key", "mimikatz", "misc::skeleton",
"sekurlsa::pth", "lsadump::lsa"
]);
let SuspiciousLSASSAccess = DeviceEvents
| where Timestamp > ago(24h)
| where ActionType == "ProcessAccessed"
| where FileName =~ "lsass.exe"
| where InitiatingProcessFileName !in~ (
"MsMpEng.exe", "csrss.exe", "werfault.exe", "taskmgr.exe",
"services.exe", "lsm.exe", "svchost.exe", "winlogon.exe"
)
| where InitiatingProcessGrantedAccessMask has_any ("0x1fffff", "0x1f3fff", "0x143a", "0x1010")
| project Timestamp, DeviceName, InitiatingProcessFileName,
InitiatingProcessCommandLine, InitiatingProcessAccountName,
GrantedAccess = InitiatingProcessGrantedAccessMask;
let DCProcessEvents = DeviceProcessEvents
| where Timestamp > ago(24h)
| where ProcessCommandLine has_any (SkeletonKeyIndicators)
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine;
union SuspiciousLSASSAccess, DCProcessEvents
| sort by Timestamp descDetects Skeleton Key-style domain controller authentication backdoor activity by monitoring for suspicious LSASS process access from unexpected processes (Sysmon Event ID 10 equivalent via DeviceEvents) and command-line indicators of Mimikatz skeleton key injection. Checks for high-privilege access masks targeting LSASS from non-system processes on domain controllers.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate endpoint detection and response (EDR) agents that access LSASS for memory scanning (e.g., CrowdStrike Falcon, Carbon Black) — verify via InitiatingProcessFileName allowlist
- Windows Error Reporting (WerFault.exe) creating LSASS dumps for debugging — check for corresponding WER entries in Event Log
- System Center Configuration Manager (SCCM) or Tanium performing inventory scans that briefly touch LSASS
- Antivirus or HIPS software performing process inspection during signature updates
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
Unlock Pro Content
Get the full detection package for T1556.001 including response playbook, investigation guide, and atomic red team tests.