Hunting For Ntlm Relay Attacks

---
name: hunting-for-ntlm-relay-attacks
description: Use when 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. Use when detecting ntlm relay attacks by analyzing windows event 4624
  logon.
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: oyi77
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
category: cybersecurity
---


# 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
**Trigger phrases:**
- "hunting for ntlm relay attacks"
- "Detect NTLM relay attacks by analyzing Windows Event 4624 logon type 3 with NTLM"


- 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


## When NOT to Use

- When you lack proper authorization for testing
- For production systems without change management
- When the task requires legal or compliance expertise beyond technical scope


## 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

1. **IP-hostname mismatch** — WorkstationName in Event 4624 does not resolve to the source IpAddress
2. **NTLMSSP authentication** — logon events using NTLM instead of Kerberos from domain-joined hosts
3. **Machine account relay** — computer accounts (ending in $) authenticating from unexpected IPs
4. **Rapid authentication** — single account authenticating to multiple hosts within seconds
5. **Named pipe access** — Event 5145 showing access to Spoolss, lsarpc, netlogon, samr pipes
6. **SMB signing disabled** — hosts not enforcing SMB signing, enabling relay attacks

## Red Flags

- Performing actions without explicit written authorization from the asset owner
- Testing against production systems without a defined scope and rules of engagement
- Exceeding the authorized scope of the engagement
- Leaving persistent access mechanisms without explicit approval
- Causing denial-of-service on production systems during testing

## Verification

- All steps executed successfully against a test environment before production use
- Output documented with screenshots or logs demonstrating expected behavior
- All exploited vulnerabilities documented with reproduction steps
- Scope boundaries confirmed — only authorized targets were tested
- Remediation recommendations included for every finding

## Output

JSON report with suspected relay events, IP-hostname correlation anomalies, SMB signing audit results, and MITRE ATT&CK mapping to T1557.001.

## Process

```python
# Example: IOC detection
import re

IOC_PATTERNS = {
    "ip": r"\b(?:\d{1,3}\.){3}\d{1,3}\b",
    "domain": r"\b[a-z0-9-]+\.[a-z]{2,}\b",
    "hash_md5": r"\b[a-f0-9]{32}\b",
    "hash_sha256": r"\b[a-f0-9]{64}\b",
}

def extract_iocs(text: str) -> dict:
    return {k: re.findall(v, text) for k, v in IOC_PATTERNS.items()}
```

1. Analyze the task requirements
2. Apply domain expertise
3. Verify output quality

## Anti-Rationalization Table

| Rationalization | Reality |
|---|---|
| "We are too small to be targeted" | Automated attacks target everyone. Size does not matter. |
| "Security slows us down" | A breach slows you down 100x more. Build security in from the start. |
| "We will fix it after launch" | Vulnerabilities in production are exploited within hours. Fix before deploy. |