Pros vs Joes CTF: The Evolution of Blue Teams

Pros v Joes CTF is a CTF that holds a special place in my heart. Over the years, I’ve moved from playing in the 1st CTF as a day-of pickup player (signing up at the conference) to a Blue Team Pro, to core CTF staff. It’s been an exciting journey, and Red Teaming there is about the only role I haven’t held. (Which is somewhat ironic given that my day job is a red team lead.) As Blue teams have just formed, and I’m not currently attached to any single team, I wanted to share my thoughts on the evolution of Blue teaming in this unique CTF. In many ways, this will resemble the Blue Team player’s guide I wrote about 3 years ago, but will be based on the evolution of the game and of the industry itself. That post remains relevant, and I encourage you to read it as well.

Basics

Let’s start by a refresher of the basics, as they exist today. The gameplay is a two day game, with teams being completely “blue” (defensive) on the first day, and teams moving to a “purple” stance (defending their own network, and able to attack each other as well) on the second day. During the first day, there’s a dedicated red team providing the offensive incentive to the blue teams, as well as a grey team representing the users/customers of the blue team services.

Each blue team consists of eight players and two pros. The role of the pros is increasingly mentorship and less “hands on keyboard”, fitting with the Pros v Joes mission of providing education & mentorship.

Scoring

Scoring was originally based entirely on Health & Welfare checks (i.e., service up and responding) and flags that can be captured from the hosts. Originally, there were “integrity” flags (submitted by blue) and offense flags (submitted by red).

As of 2017, scoring included health & welfare (service uptime), beacons (red cell contacting the scoreboard from the server to prove that it is compromised), flags (in theory anyway), and an in-game marketplace that could have both positive and negative effects. 2018 scoring details have not yet been released, but check the 2018 rules when published.

The Environment

The environment changes every year, but it’s a highly heterogenous network with all of the typical services you would find in a corporate network. At a minimum, you’re likely to see:

  • Typical web services (CMS, etc.)
  • Mail Server
  • Client machines
  • Active Directory
  • DNS Server

The operating systems will vary, and will include older and newer OSs of both Windows and Linux varities. There has also always been a firewall under the control of each team segregating that team’s network from the rest of the network. These have been both Cisco ASA firewalls as well as pfSense firewalls.

Each player connects to the game environment using OpenVPN based on configurations and credentials provided by Dichotomy.

Preparation

There has been an increasing amount of preparation involved in each of the years I have participated in PvJ. This preparation has essentially come in two core forms:

  1. Learning about the principles of hardening systems and networks.
  2. Preparing scripts, tools, and toolkits for use during the game.

Fundamentals

It turns out that a lot of the fundamental knowledge necessary in securing a network are just basically system administration fundamentals. Understanding how the system works and how systems interact with each other provides much of the basics of information security.

On both Windows and Linux, it is useful to understand:

  • How to install & update software and operating system updates
  • How to change permissions of files
  • How to start and stop services
  • How to set up a host-based firewall
  • Basic Shell Commands
  • User administration

Understanding basic networking is also useful, including:

  • TCP vs UDP
  • Stateful vs stateless firewalls
  • Using tcpdump and Wireshark to debug and understand network traffic

Knowing some kind of scripting language as well can be very useful, especially if your team prepares some scripts in advance for common operations. Languages that I’ve found useful include:

  • Bash
  • Powershell
  • Python

Player Toolkit

Obviously, if you’re playing in a CTF, you’ll need a computer. Many of the tools you’ll want to use are either designed for Linux or are more commonly used on Linux, so almost everyone will want to have some sort of a Linux environment available. I suggest that you use whatever operating system you are most comfortable with as your “bare metal” operating system, so if that’s Windows, you’ll want to run a Linux virtual machine.

If you use a Macbook (which seems to be the most common choice at a lot of security conferences), you may want both a Windows VM and a Linux VM, as the Windows Server administration tools (should you choose to use them) only run on Windows clients. It’s also been reported that TunnelBlick is the best option for an OpenVPN Client on MacOS.

As to choice of Linux distribution, if you don’t have any personal preference, I would suggest using Kali Linux. It’s not that Kali has anything you can’t get on other distributions, but it’s well-known in the security industry, well documented, and based on Debian Linux, which makes it well-supported and a close cousin of Ubuntu Linux that many have worked with before.

There are some tools that are absolutely necessary and you should familiarize yourself with them in advance:

  • nmap for network enumeration
  • SSH for connecting to Linux Machines
  • RDP for connecting to Windows Machines
  • git, if your team will use it for managing configurations or scripts
  • OpenVPN for connecting to the game environment

Other tools you’ll probably want to get some experience with:

  • metasploit for going offensive
  • Some kind of directory enumeration tool (Dirbuster, WebBorer)
  • sqlmap for SQL injection

Useful Resources

Game Strategy

Every team has their own general strategy to the game, but there are a few things I’ve found that seem to make gameplay go more smoothly for the team:

  • During initial hardening, have one team member working on the firewall. Multiple players configuring the firewall is a recipe for lockouts or confusion.
  • Communicate, communicate, communicate. Ask questions when needed, and make sure it’s clear who’s working on what.
  • Document everything you do. You don’t need to log every command (though it’s not a bad idea), but you should be able to answer some questions about the hosts in your network:
    • What hosts exist?
    • What are the passwords for the accounts?
    • Have the passwords been changed from the defaults?
    • What services are scored?
    • What hardening steps have been applied?

Dos & Don’ts

  • DO make sure you have a wired ethernet port on your laptop, or a USB to ethernet adapter and an ethernet cable.
  • DO make sure you’ve set up OpenVPN on your host OS (not in a VM) and you’ve tested it before game day.
  • DO make sure you’ve read the rules. DON’T try to cheat, Gold team will figure it out and make you pay.
  • DO make an effort to try new things. This game is a learning experience, and you miss 100% of the shots you don’t take.
  • DO ask questions. DON’T be afraid of looking stupid – everyone in the security industry has things to learn, and the whole point of this event is that you can learn. You might even stump the pros.

Making the Most of It

Like so many things in life, the PvJ CTF is a case where you get out of it what you put into it. If you think you can learn it all by osmosis or being on the same team but without making effort, it’s unlikely to work out. PvJ gives you an enthusiastic team, mentors willing to help, and a top-notch environment to try things out that you might not have the resources for in your environment.

To all the players: Good luck, learn new things, and have fun!


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Introduction

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