Mastering the OffSec Gauntlet: A Complete Tutorial Walkthrough

A comprehensive guide to understanding OffSec's Grimoire challenges and answer formats

Introduction

The OffSec Gauntlet represents a significant evolution in penetration testing education, moving beyond traditional multiple-choice questions to real-world forensic analysis and incident response scenarios. This walkthrough covers the complete tutorial series that prepares you for the Grimoire challenges - where precision, methodology, and attention to detail are paramount.

Whether you're preparing for OSCP, diving into advanced penetration testing, or honing your incident response skills, understanding these exercise formats is crucial for success in modern cybersecurity assessments.

Exercise 1: Basic Answer Formatting

The Challenge

The tutorial begins with a fundamental concept: answer format flexibility. You're tasked with identifying attacker IP addresses from forensic analysis:

  • 192.168.50.1
  • 192.168.50.2
  • 192.168.50.3

Accepted Formats

Comma-separated:

192.168.50.1, 192.168.50.2, and 192.168.50.3

Space-separated:

192.168.50.1 192.168.50.2 192.168.50.3

Text format:

The first IP address used by the attacker is 192.168.50.1. The second one is 192.168.50.2 and the third one is 192.168.50.3.

List format:

- 192.168.50.1 
- 192.168.50.2 
- 192.168.50.3

Key Takeaway

All formats are valid as long as they contain the complete, accurate information. Choose the format that best suits your communication style and the complexity of the answer required.

Exercise 2: Contextual Analysis

Enhanced Requirements

This exercise builds on the previous one by requiring both IP identification and purpose explanation:

  • 192.168.50.1 → File exfiltration
  • 192.168.50.2 → C2 communication
  • 192.168.50.3 → Phishing campaigns

Solution Examples

Structured List Format:

- 192.168.50.1 – exfiltrating files  
- 192.168.50.2 – C2 communication  
- 192.168.50.3 – sending phishing emails

Narrative Format:

192.168.50.1 was used for exfiltrating files, 192.168.50.2 for C2 communication, and 192.168.50.3 for sending phishing emails.

Common Pitfalls

❌ Adding extra IPs:

- 192.168.50.1 – exfiltrating files  
- 192.168.50.2 – C2 communication  
- 192.168.50.3 – sending phishing emails  
- 192.168.50.4 - downloading malware  // INCORRECT

❌ Duplicate entries:

- 192.168.50.1 – exfiltrating files  
- 192.168.50.2 – C2 communication  
- 192.168.50.3 – sending phishing emails  
- 192.168.50.3 - sending phishing emails  // DUPLICATE

Exercise 3: Complex Attack Chain Reconstruction

Advanced Scenario Analysis

Real-world incident response often requires reconstructing complete attack chains. The tutorial presents this scenario:

Describe how code execution was achieved on the target system COMP1. Begin with the initial access vector and walk through each step leading to the execution of a ransomware binary. Your answer must include exact information of any URLs, usernames, email addresses, filenames, IP addresses, commands, or scripts involved.

Methodology: The Kill Chain Approach

Sample Attack Scenario:

  1. Initial Access: Phishing email with malicious link
  2. Execution: HTML smuggling delivers ISO file
  3. Persistence: Ransomware loader execution
  4. Impact: Final payload deployment

Solution Format Options

Narrative Style:

The user [email protected] received an email from [email protected] containing a link to https://thisisjustatest123123123.com, which automatically downloaded the file trial.iso via HTML smuggling. The user followed the instructions in the email to mount the ISO and executed notransomware.exe. This file then downloaded an archive from https://thisisjustatest123123123.blobl.core.windows.net/notransomware/really-not-ransomware.zip to C:\Users\daniel.duesentrieb\Documents\really-not-ransomware.zip. The loader notransomware.exe extracted really-not-ransomware.exe into the same directory and executed it.

Structured Analysis:

Initial Access:
- Email sent from [email protected] to [email protected]
- Email included a link to https://thisisjustatest123123123.com with instructions to visit it
- Website used HTML smuggling to download the ISO file trial.iso

Loader Execution:
- User mounted trial.iso and executed notransomware.exe (as instructed in the phishing email)
- notransomware.exe downloaded really-not-ransomware.zip to:
  C:\Users\daniel.duesentrieb\Documents\really-not-ransomware.zip
- Archive was downloaded from:
  https://thisisjustatest123123123.blobl.core.windows.net/notransomware/really-not-ransomware.zip

Ransomware Execution:
- User extracted really-not-ransomware.exe from the archive into the same directory
- Loader executed really-not-ransomware.exe, triggering the ransomware

Pro Tip

For newcomers to cybersecurity, the structured format is recommended. It ensures all required components are included and makes your analytical process clear and verifiable.

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