Tool Roundup: Top Open Source C2 Frameworks for Modern Red Teaming
When Cobalt Strike dominated the offensive security market, running a command and control (C2) server meant one of two things: you either had the budget to afford a commercial license, or you were wrestling with clunky, unstable open-source scripts. That dynamic has entirely shifted.
Over the last few years, the open-source community has engineered C2 frameworks that rival—and in some cases, outpace—commercial offerings in evasion, modularity, and operational security. If you are conducting authorized adversary simulation or trying to test your SOC's detection capabilities, relying on default Metasploit payloads will not cut it. You need modern tools designed to bypass EDRs via sleep obfuscation, indirect syscalls, and malleable profiles.
Let's break down three of the most capable open-source C2 frameworks available today, when you should reach for them, and how they stack up.
The Job to Be Done: Covert Post-Exploitation
A Command and Control (C2) framework is the nerve center of a red team engagement. Once initial access is achieved (perhaps using techniques from our Active Directory Exploitation Methodology), you need a way to maintain access, execute commands, pivot laterally, and exfiltrate data without triggering a dozen high-severity alerts on the defender's EDR dashboard.
The criteria for a strong C2 framework are:
- OpSec & Evasion: Does the agent (implant) support memory evasion techniques like sleep obfuscation?
- Customization: Can you alter network signatures (malleable C2) easily?
- Collaboration: Can multiple red team operators use the same server concurrently?
A high-tech matrix comparing various C2 framework agents communicating securely with their central teamservers.
1. Havoc
The Modern Cobalt Strike Alternative
If you want a framework that looks, feels, and operates like a premium commercial C2 out of the box, Havoc is currently the gold standard. Written in Go and C/C++, Havoc boasts a sleek, Qt-based graphical interface that makes managing multiple compromised endpoints intuitive.
Havoc's default agent, "Demon," is heavily focused on evasion. It supports indirect syscalls, return address spoofing, and Ekko/FOLIAGE sleep obfuscation techniques, making it remarkably difficult for standard EDRs to catch in memory.
Usage Example: Starting the Havoc Teamserver and configuring a listener profile.
# Start the teamserver with a custom profile (assuming you have compiled Havoc) ./havoc server --profile profiles/havoc_default.yaotl -v --debug # Inside the Havoc client UI, you would configure your listener. # A typical malleable profile snippet in Havoc looks like this: Teamserver { Host = "0.0.0.0" Port = 40056 Build { Compiler64 = "x86_64-w64-mingw32-gcc" Compiler86 = "i686-w64-mingw32-gcc" } }
When to reach for it: Use Havoc for high-stealth, full-scope red team engagements where bypassing modern Windows EDRs is the primary objective.
2. Mythic
The Modular Behemoth
Mythic takes a vastly different architectural approach. Instead of building one monolithic tool, Mythic is entirely modular and "plug-and-play." Built around Docker, PostgreSQL, and RabbitMQ, the core Mythic server acts as a centralized routing hub. You do not get any agents or C2 network profiles by default; you must install them from the community repository.
This modularity is its superpower. You can write an agent in Python for a macOS target, an agent in C# for Windows, and an agent in Go for Linux—all communicating back to the same Mythic web interface through completely different protocols (HTTP, DNS, SMB).
Usage Example: Installing an agent (like Apollo) and a C2 profile via the mythic-cli.
# From your Mythic installation directory sudo ./mythic-cli install github https://github.com/MythicAgents/Apollo.git sudo ./mythic-cli install github https://github.com/MythicC2Profiles/http.git # Restart Mythic to apply the new agent and profile containers sudo ./mythic-cli restart
When to reach for it: Use Mythic in complex, multi-OS environments (macOS, Linux, Windows) where you need distinct agents and highly customized communication channels (e.g., routing C2 traffic through Slack or GitHub APIs).
3. Covenant
The .NET Powerhouse
Covenant is built specifically for offensive .NET tradecraft. Its agents, called "Grunts," are written in C# and execute payloads dynamically in memory. Covenant's web interface is excellent for operators who want to rapidly deploy modules from tools like Rubeus, Seatbelt, or SharpHound without dropping binaries to disk.
However, Covenant has a limitation: because it is widely known and strictly .NET-focused, its default behaviors (like Assembly.Load injection techniques) are highly signatured by modern AVs. Unless you are heavily modifying the agent templates, you will struggle against top-tier EDRs.
Usage Example: Running a Covenant Docker container for a quick engagement setup.
# Clone the repository and run via Docker git clone --recurse-submodules https://github.com/cobbr/Covenant cd Covenant/Covenant docker build -t covenant . docker run -it -p 7443:7443 -p 80:80 -p 443:443 --name covenant -v $(pwd)/Data:/app/Data covenant
When to reach for it: Use Covenant in environments with minimal EDR visibility, or during "assume-breach" purple team exercises where you specifically want to test the SOC's ability to detect in-memory .NET execution.
The Verdict: What I'd Actually Use
If I am spinning up infrastructure for an engagement today, my immediate choice is Havoc (or Sliver, which we covered deeply in our Sliver C2 Framework Spotlight). Havoc's out-of-the-box memory evasion techniques save countless hours of payload development, and the interface allows for rapid tasking during high-stress operations.
Mythic is incredible for research and specialized cross-platform engagements, but the overhead of managing multiple Docker containers and troubleshooting disparate community agents can slow down a fast-paced assessment. Covenant remains a fantastic learning tool for .NET exploitation, but it requires too much customization for modern stealth operations.
Ethics Reminder: The usage of C2 frameworks is exclusively for authorized red team engagements, penetration tests, and defensive adversary simulation. Deploying these agents against networks you do not own or have explicit permission to test is a severe legal violation. Use these tools to make defenders better, not to cause chaos.
References / Further reading
- C5pider. "Havoc Framework Official Repository." GitHub, https://github.com/HavocFramework/Havoc.
- its-a-feature. "Mythic C2 Framework Repository." GitHub, https://github.com/its-a-feature/Mythic.
- Mythic Developers. "Mythic Documentation." Mythic C2, https://docs.mythic-c2.net/.
- cobbr. "Covenant C2 Framework Repository." GitHub, https://github.com/cobbr/Covenant.
