| name | hunting-for-ntlm-relay-attacks |
| description | Detect NTLM relay attacks by analyzing Windows Event 4624 logon type 3 with NTLMSSP authentication, identifying IP-to-hostname mismatches, Responder traffic signatures, SMB signing status, and suspicious authentication patterns across the domain. |
| domain | cybersecurity |
| subdomain | threat-hunting |
| tags | ["NTLM-relay","Windows-events","Event-4624","NTLMSSP","Responder","SMB-signing","credential-access","T1557.001","Active-Directory"] |
| version | 1.0 |
| author | mahipal |
| license | Apache-2.0 |
| d3fend_techniques | ["Application Protocol Command Analysis","Network Isolation","Network Traffic Analysis","Client-server Payload Profiling","Network Traffic Community Deviation"] |
| nist_csf | ["DE.CM-01","DE.AE-02","DE.AE-07","ID.RA-05"] |
Hunting for NTLM Relay Attacks
Overview
NTLM relay attacks intercept and forward NTLM authentication messages to gain unauthorized access to network resources. Attackers use tools like Responder for LLMNR/NBT-NS poisoning and ntlmrelayx for credential relay. This skill detects relay activity by querying Windows Security Event 4624 (successful logon) for type 3 network logons with NTLMSSP authentication, identifying mismatches between WorkstationName and source IpAddress, detecting rapid multi-host authentication from single accounts, and auditing SMB signing configuration across domain hosts.
When to Use
- When investigating security incidents that require hunting for ntlm relay attacks
- When building detection rules or threat hunting queries for this domain
- When SOC analysts need structured procedures for this analysis type
- When validating security monitoring coverage for related attack techniques
Detection Gaps & Validation
- Same-subnet relays defeat the IP-hostname mismatch. When the relay source and victim share a subnet (or the attacker preserves
WorkstationName), the 4624 WorkstationName-vs-IpAddress check produces no anomaly.
- SMB-signing audit covers only SMB. LDAP and HTTP relay paths — notably AD CS web enrollment (ESC8) and PetitPotam/PrinterBug coercion — are missed. Watch 4624 Type 3 NTLMSSP targeting the CA enrollment host.
- Kerberos-only environments are still vulnerable via authentication coercion (PetitPotam EFSRPC, PrinterBug Spoolss): hunt Event 5145 named-pipe access to
\pipe\efsrpc, \pipe\spoolss, \pipe\lsarpc, \pipe\netlogon, \pipe\samr.
- Validate the hunt fires: in a lab run
Responder + ntlmrelayx.py (or a coercer like PetitPotam.py) and confirm 4624 LogonType 3 with AuthenticationPackageName=NTLM, a WorkstationName≠resolved-IP, and 5145 pipe access all appear and alert.
- FP tuning: legacy apps and scanners that still use NTLM, plus NAT/load-balancers that legitimately cause IP-hostname mismatches — whitelist by known service accounts and source ranges.
Prerequisites
- Python 3.9+ with Windows Event Log access or exported logs
- Windows Security audit logging enabled (Event ID 4624, 4625, 5145)
- Network access for SMB signing status checks
Key Detection Areas
- — WorkstationName in Event 4624 does not resolve to the source IpAddress
