Detect Kerberoasting in Splunk
Adversaries may abuse a valid Kerberos ticket-granting ticket (TGT) to request Kerberos ticket-granting service (TGS) tickets for any service principal name (SPN) registered in Active Directory. Portions of these tickets encrypted with RC4 (etype 0x17) use the service account's NTLM hash as the private key, making them vulnerable to offline brute force attacks using tools like Hashcat or John the Ripper. Cracked credentials enable persistence, privilege escalation, and lateral movement via valid domain accounts. Common tooling includes Rubeus, Invoke-Kerberoast (PowerSploit/Empire), Impacket GetUserSPNs.py, SILENTTRINITY, and Brute Ratel C4. Confirmed threat actor usage includes Wizard Spider (Ryuk ransomware campaigns), FIN7, and Indrik Spider.
MITRE ATT&CK
- Tactic
- Credential Access
- Technique
- T1558 Steal or Forge Kerberos Tickets
- Sub-technique
- T1558.003 Kerberoasting
- Canonical reference
- https://attack.mitre.org/techniques/T1558/003/
SPL Detection Query
index=wineventlog sourcetype="WinEventLog:Security" EventCode=4769
NOT TargetUserName="*$"
NOT ServiceName="*$"
NOT ServiceName="krbtgt"
TicketEncryptionType="0x17"
| eval NormalizedSourceIP=replace(IpAddress, "::ffff:", "")
| stats
count as TGSRequestCount,
dc(ServiceName) as UniqueServiceCount,
values(ServiceName) as TargetSPNs,
earliest(_time) as FirstSeen,
latest(_time) as LastSeen
by TargetUserName, NormalizedSourceIP, host
| eval IsBulkKerberoast=if(UniqueServiceCount >= 5, "true", "false")
| eval AlertPriority=case(
UniqueServiceCount >= 20, "Critical",
UniqueServiceCount >= 5, "High",
1=1, "Medium")
| sort - UniqueServiceCount - TGSRequestCount
| table FirstSeen, LastSeen, host, TargetUserName, NormalizedSourceIP, TGSRequestCount, UniqueServiceCount, IsBulkKerberoast, AlertPriority, TargetSPNsDetects Kerberoasting via Splunk Windows Security event logs by identifying EventCode 4769 (Kerberos Service Ticket Request) with RC4-HMAC encryption type (0x17). Filters out machine accounts and the krbtgt service to reduce noise. Aggregates per requesting user and source IP to surface bulk kerberoasting patterns typical of automated tools like Rubeus or Invoke-Kerberoast. Alert priority scales with unique SPN count — five or more unique SPNs in a session window strongly indicates automated tooling.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Legacy applications requiring RC4 Kerberos encryption due to compatibility constraints — validate source IPs against known legacy application inventory
- Security scanning tools performing AD enumeration as part of scheduled assessments — correlate with scan schedules
- Enterprise applications (Oracle, SAP) configured to use RC4 — these generate consistent low-volume RC4 requests from fixed source IPs
- Authorized penetration testing exercises — verify against change management records
- AD management software that programmatically requests service tickets for connectivity verification
Other platforms for T1558.003
Testing Methodology
Validate this detection against 4 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 1Invoke-Kerberoast via PowerSploit — Bulk Hash Extraction
Expected signal: Domain Controller Security Event ID 4769 for each SPN enumerated with TicketEncryptionType=0x17. Sysmon Event ID 1 on source host: powershell.exe with 'Invoke-Kerberoast' in CommandLine. Sysmon Event ID 3: TCP connection to DC on port 88 (Kerberos). PowerShell ScriptBlock Event ID 4104 with full Invoke-Kerberoast script content (deobfuscated). Sysmon Event ID 11: file creation for kerberoast_hashes.txt.
- Test 2Rubeus Kerberoast — All Roastable Accounts
Expected signal: Domain Controller Security Event ID 4769 for each SPN with TicketEncryptionType=0x17. Sysmon Event ID 1: Rubeus.exe process creation with 'kerberoast' argument. Sysmon Event ID 3: TCP connection to DC on port 88. Sysmon Event ID 11: file creation for rubeus_hashes.txt. Windows Defender may independently generate alerts for Rubeus.exe based on signature detection.
- Test 3Impacket GetUserSPNs — Linux-Based Kerberoasting
Expected signal: Domain Controller Security Event ID 4769 for each SPN with TicketEncryptionType=0x17, IpAddress field contains the Linux host IP. Event ID 4768 (TGT request) from Linux host IP preceding the 4769 events. No Sysmon telemetry (Linux source). DC Security logs capture the full activity. The source IP not matching any domain-joined Windows workstation is a high-fidelity anomaly indicator.
- Test 4Targeted Single-SPN Request via .NET KerberosRequestorSecurityToken
Expected signal: Domain Controller Security Event ID 4769: ServiceName=MSSQLSvc/sql01.corp.local:1433, TicketEncryptionType=0x17 (if target service account supports RC4). Sysmon Event ID 1: powershell.exe with 'KerberosRequestorSecurityToken' in CommandLine. PowerShell ScriptBlock Event ID 4104 with full .NET reflection code. Note: If the target account enforces AES-only encryption, EncryptionType will be 0x12 and detection will not fire on the RC4 rule — the account is not kerberoastable.
References (10)
- https://attack.mitre.org/techniques/T1558/003/
- https://blogs.technet.microsoft.com/motiba/2018/02/23/detecting-kerberoasting-activity-using-azure-security-center/
- https://adsecurity.org/?p=2293
- https://blog.harmj0y.net/powershell/kerberoasting-without-mimikatz/
- https://github.com/GhostPack/Rubeus
- https://github.com/fortra/impacket/blob/master/examples/GetUserSPNs.py
- https://learn.microsoft.com/en-us/windows/security/threat-protection/auditing/event-4769
- https://redsiege.com/kerberoast-slides
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1558.003/T1558.003.md
- https://www.crowdstrike.com/blog/meet-carbon-spider/
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