What are C2 Frameworks? The Foundation of Cyberattacks

Command and control (C2) frameworks are essential tools in modern cyberattacks, allowing threat actors to communicate with compromised systems. 

CISA reports that ransomware groups, including Conti and LockBit, heavily rely on C2 channels to coordinate attacks, steal credentials, and exfiltrate data before encryption. This setup allows attackers to control multiple stages of an attack while evading detection. Proactively monitoring C2 traffic is crucial to intercept these threats before they escalate.

In this article, we will cover how C2 frameworks operate, their role in modern attacks, and strategies to detect and mitigate these threats.

How C2 Frameworks Work

C2 frameworks operate as a communication channel between an attacker and the compromised system. These frameworks use a client-server model where the attacker controls a central server to manage multiple infected systems. Once malware infects a device, it connects back to the C2 server, awaiting commands. These communications are often encrypted to evade detection by security systems.

The attacker can remotely send instructions to the infected system, such as extracting data or moving laterally within a network. By using multiple C2 frameworks, attackers can improve their chances of avoiding detection, allowing them to evaluate the security defenses of a target more thoroughly.

Here's a quick breakdown:

1. Initial Infection: the attacker gains access to the target, often through malware or phishing campaigns.
2. Connection Established: the infected system reaches out to the C2 server for further instructions.
3. Command Execution: the attacker sends commands to the infected system to perform actions like gathering data or spreading to other systems.

What is a C2 Framework?

A C2 (Command and Control) framework, is an advanced platform hackers use to control and manage compromised systems remotely. It's a central hub where they can manage hundreds of compromised systems in a target network. 

These frameworks offer advanced automation, allowing attackers to perform post-exploitation tasks like lateral movement, privilege escalation, and persistence. 

Typically a C2 framework consists of three parts: 

1. C2 server 
2. C2 client
3. C2 agent 

The C2 server is the command center, the client is the interface used by the attacker, and the agent is the software installed on the compromised systems to facilitate communication. Endpoint monitoring is key to detecting activity on compromised systems.

C2 Server

The C2 server is the central command center. Think of it as the hub where the attacker orchestrates everything—issuing commands, managing connections, and storing logs.

Attackers can host their C2 servers in a few different ways:

• Dedicated infrastructure: This could be self-hosted servers or virtual private servers (VPS).
• Cloud services: Platforms like AWS or Azure are often used because they blend in with normal traffic.
• Compromised servers: Sometimes attackers hijack someone else’s infrastructure to avoid being traced.

What does the C2 server actually do?

• It manages all connections to compromised systems.
• Sends commands for things like data theft, lateral movement, or deploying additional malware.
• Acts as the communication hub for multiple infected systems.

C2 Client

The C2 client is what the attacker uses to interact with the server. It’s essentially the dashboard or interface where they run the show.

Here’s what the client enables attackers to do:

• Issue commands: They can tell infected systems to collect files, execute tasks, or spread malware.
• Automate tasks: Many modern C2 tools allow automation, saving attackers time on repetitive activities.
• Monitor in real time: Attackers get live updates on what’s happening across compromised systems.
• Customize attacks: Many C2 frameworks let attackers write scripts or add plugins to adapt to specific targets.

For attackers, this interface makes the job simple and efficient, whether they’re stealing data or testing a company’s security defenses.

C2 Agent

The C2 agent is the small piece of software installed on the compromised systems. It’s what connects the infected device back to the C2 server and carries out the attacker’s commands.

How does it work?

• First contact: Once a system is infected, the agent “calls back” to the C2 server. This can happen through encrypted web traffic (like HTTPS), DNS tunneling, or other covert channels.
• Execution: The agent waits for instructions and then executes commands—whether it’s stealing files, running scripts, or moving through the network.
• Staying hidden: Agents are designed to be stealthy. They often mimic legitimate processes (like “svchost.exe”) or use fileless malware techniques to stay under the radar.

Common examples of C2 agents:

• Cobalt Strike’s Beacon: A flexible and modular agent used for post-exploitation tasks.
• PowerShell payloads: Lightweight scripts that are perfect for fileless attacks.
• HTTP-based agents: These use everyday web protocols to blend in with legitimate network traffic.

Purpose and Benefits of C2 Frameworks

The purpose of command and control frameworks is to perform post-exploitation, maintain access to compromised systems, and enable collaboration between attackers. One of the benefits of using a C2 framework is to manage compromised systems from a central location, it's more efficient and streamlined.

Also, these frameworks offer robust ways to interact with compromised systems, so threat actors and red teams can customize the C2 infrastructure to specific targets or objectives. Another big advantage is to evade detection and be stealthy, which is key to long-term cyber operations. Anomaly detection can help detect unusual patterns of behavior of C2 framework activity.

Types of C2 Frameworks

Command and control frameworks fall into two categories:

• Custom-built C2 frameworks: some threat actors, especially nation-state groups, build their own C2 frameworks to evade detection.

• Off-the-shelf tools: Cobalt Strike, Metasploit, and Empire are popular tools attackers use because they are easy to use and effective. Knowing the popular C2 frameworks is key to choosing the right tool for your project and getting hands-on experience with them.

Popular C2 Frameworks

C2 frameworks are widely used in the cybersecurity industry for various purposes, including penetration testing, red teaming, and security research. Here are some popular C2 frameworks:

• Cobalt Strike: a commercial adversary simulation and red team operations platform widely used in the security industry. Known for its flexibility and powerful features, Cobalt Strike is a favorite among professionals for simulating advanced threats and managing compromised systems.

• PowerShell Empire: an open-source post-exploitation framework that extensively uses the PowerShell scripting language. It is highly regarded for its ability to automate complex tasks and execute commands on compromised systems, making it a valuable tool for penetration testers and red teamers.

• Sliver: an open-source, cross-platform adversary emulation and red team framework designed for security testing. Sliver is gaining popularity due to its stealth and adaptability, allowing users to simulate sophisticated C2 attacks and evade detection.

• Havoc: a free, open-source C2 framework that provides a client interface for interacting with the C2 server in real time through API calls. Havoc is known for its user-friendly interface and advanced automation capabilities, making it an excellent choice for managing compromised systems.

• Brute Ratel C4: a commercial red team and adversary simulation platform that can automate the execution of adversary tactics, techniques, and procedures (TTPs). Brute Ratel C4 is designed to mimic real-world attacks, providing a realistic and challenging environment for testing defenses.

These popular C2 frameworks offer a range of features and capabilities, making them essential tools for red team operations and penetration testing.

Why C2 Frameworks Matter in Attacks

Command and control frameworks are part of the cyber kill chain. After initial access, attackers use C2 to control the infected systems. For example in ransomware attacks C2 allows the attacker to distribute the encryption keys. In Advanced Persistent Threat (APT) campaigns they help with long-term espionage and data theft.

Behavioral analysis, using C2 feeds, and Network analysis can help detect C2 framework activity by looking for anomalies.

Challenges in Detecting C2 Activity

Spotting Command and Control (C2) activity in a network is no easy task. Attackers have gotten smarter, disguising their communication to look like normal traffic. Most modern C2 frameworks use everyday protocols like HTTP/HTTPS, DNS, or even email (SMTP) to stay hidden. Since businesses rely heavily on these protocols, blocking or flagging suspicious traffic often risks disrupting legitimate operations. This puts security teams in a tough spot—how do you separate the malicious from the ordinary without constantly crying wolf?

Another major challenge is encryption. Today’s C2 tools encrypt their communications to hide the content from detection systems. For instance, platforms like Cobalt Strike or Sliver send commands over secure channels, blending in with normal encrypted web traffic. Without advanced tools to inspect encrypted data or analyze behavioral patterns, this kind of activity can easily slip past traditional defenses.

Attackers also rely on obfuscation techniques to cover their tracks. They might use tricks like domain fronting (routing traffic through well-known services like content delivery networks), impersonating legitimate protocols, or deploying polymorphic malware that constantly changes its form. Because these techniques make the C2 communication dynamic, signature-based detection tools often fall short—they simply can’t keep up with constantly shifting patterns.

To make matters even trickier, attackers often layer their setups with redirectors or multi-stage C2 servers. Tools like RedGuard, for example, act as a go-between, funneling traffic from compromised systems to the actual C2 server. This masks the origin and makes tracking the real infrastructure a guessing game. For defenders, relying on a single detection method won’t cut it. It takes a combination of network analysis, endpoint monitoring, and real-time threat intelligence to piece together the subtle clues that reveal C2 activity.

How to Find C2 Frameworks

Finding command and control frameworks is tough because attackers will use all sorts of tricks to hide. But here's how you can spot them:

1. Open Directories Counterintelligence: track exposed directories with AttackCapture™, which flags potential C2 staging points hidden in overlooked open directories, keeping them from being used against you. 

2. Threat Intelligence Feed: access updated intelligence on known C2 servers through our C2 Feed, ensuring your defenses stay proactive against the latest threats with actionable, real-time data.

3. Threat Hunting API: enrich investigations with our Threat Enrichment API, providing deep context around C2 indicators for faster, more accurate detection and response.

4. Network Traffic Monitoring: look for unusual outgoing traffic, especially to unknown or suspicious IP addresses. C2 is where attackers connect to execute remote commands and manage compromised machines. Integration with SIEM will give you real-time monitoring and analysis of network traffic.

5. Behavioral Analysis: look for weird behavior in your systems that might indicate C2 communication.

6. Real-time Threat Intelligence: stay up to date with new C2 frameworks so you can block them before they hit.

Detection Methods

Detecting command and control frameworks is tough because they can blend in with normal network traffic. But here are some methods to help identify and detect them:

• Network Traffic Analysis: by analyzing network traffic patterns, security teams can see suspicious communication between a compromised machine and a C2 server. Unusual outgoing traffic to unknown IP addresses or domains is a red flag.

• Endpoint Monitoring: monitoring endpoint activity is key to detecting malicious activity on compromised systems. Tools that track changes to system files, registry entries, and running processes can spot anomalies indicative of C2 framework activity.

• Anomaly Detection: unusual patterns of behavior on a network or system are a sign of the C2 framework. This includes unexpected data transfers, irregular login times, and other deviations from normal activity.

• Signature-Based Detection: signature-based detection tools can help identify known C2 frameworks and their associated malware. These tools rely on a database of known signatures to match against observed activity.

• Behavioral Analysis: analyzing a system or network can help identify potential C2 framework activity. This means looking for behavior that's out of the norm, like repeated failed login attempts or unusual command executions.

By using these detection methods, you can better detect and mitigate C2 framework risks and get compromised systems detected and fixed faster.

Real-life examples of how to detect C2 frameworks

Here at Hunt.io, we're dedicated to shining a light on the shadowy networks of Command and Control (C2) frameworks. 

Here's a glimpse into some of our deep-dive investigations that reveal insights into how adversaries exploit these powerful tools.

1. Detecting SuperShell and Cobalt Strike from an Open Directory - In one of our deep investigations, we unearthed details of SuperShell and Cobalt Strike within an open directory. By analyzing specific C2 setups and communication protocols, we've outlined key indicators, helping defenders recognize and disrupt these infrastructures as they emerge in the wild​.

1. Viper's Versatility Paired with Cobalt Strike - Our tracking shows how Viper, a highly modular C2 tool, is frequently integrated with Cobalt Strike and Sliver. With over 400 IP addresses in our system hosting Viper panels, we're able to map out its extensive reach and the technical configurations that make it a favorite for adversaries​

2. RedGuard as a C2 Redirector - We've also turned our attention to RedGuard, which often acts as a shield for primary C2 servers by redirecting traffic that confuses investigators. By documenting RedGuard's specific fingerprints and port usage, we're building a knowledge base that aids in early detection of these stealthy setups​

3. Tracking SparkRAT - SparkRAT's cross-platform capabilities make it a formidable player in the C2 ecosystem. Through our analysis, we've noted common characteristics, like port configurations and login methods, which help in pinpointing SparkRAT servers before they escalate attacks​

4. Exposed Red Team Tools: Havoc, Cobalt Strike, and Villain - Our hunt through an open directory revealed a trove of red team tools, including configurations for Cobalt Strike and Havoc. These findings help us continually refine our threat detection rules to recognize similar C2 setups, providing real-time insights into how attackers configure their malicious frameworks​

With the right tools and data, spotting and neutralizing C2 frameworks becomes achievable, keeping defenders one step ahead in an ever-evolving cyber landscape. Book a demo to see how our threat-hunting platform empowers teams with real-time insights and detection rules to identify and disrupt adversary infrastructure before it escalates.

Multiple C2 Frameworks

Using multiple C2 frameworks is a common practice in red team operations and penetration testing. This approach allows users to expand their options and achieve due diligence. Here are some benefits of using multiple C2 frameworks:

• Increased Flexibility: Using multiple C2 frameworks provides users with increased flexibility and options for managing compromised systems. Different frameworks offer unique features and capabilities, allowing users to choose the best tool for each specific task.

• Improved Evasion: Using multiple C2 frameworks can improve evasion techniques and make it more difficult for defenders to detect and respond to attacks. By switching between different frameworks, attackers can avoid patterns that might be recognized by threat hunting tools.

• Enhanced Realism: Using multiple C2 frameworks can enhance the realism of red team operations and penetration testing, making it more challenging for defenders to detect and respond to attacks. This approach helps simulate a variety of threat scenarios, providing a comprehensive assessment of an organization's defenses.

Some popular open-source C2 frameworks used in multiple-framework-based attacks are:

• Covenant: a collaborative C2 framework designed for red teaming assessments. Covenant is known for its ease of use and powerful features, making it a popular choice for security professionals.

• Sillenttrinity: an asynchronous and multi-server command and control framework. Sillenttrinity is designed to be stealthy and flexible, allowing users to manage compromised systems effectively.

• Koadic: a Windows post-exploitation framework. Koadic is highly regarded for its ability to execute complex tasks on compromised Windows systems, making it a valuable tool for post-exploitation activities.

• Merlin: a C2 framework that uses HTTP/1.1, HTTP/2, and HTTP/3 protocols to evade detection. Merlin's use of modern communication protocols makes it difficult for defenders to identify and block its traffic.

By leveraging the strengths of different C2 frameworks, red teams can simulate complex attacks and find weaknesses in an organization's defenses, ultimately improving overall security.

C2 Frameworks in Red Team

Command and control frameworks are an essential tool in red teaming, to simulate real-world attacks and test an organization's defenses. In red team engagements, multiple C2 frameworks are used to have more options and due diligence. By using different C2 frameworks, red teams can mimic the tactics, techniques, and procedures (TTPs) of various threat actors, to have a comprehensive view of an organization's security posture. Integration with incident response tools to take action fast when a threat is detected.

Red Team Toolbox

A command and control framework is a must-have in the red team toolbox, to communicate with compromised devices and execute post-exploitation. The C2 framework is used to drop payloads or tools to assist with various activities, like running commands on the compromised device, bypassing antivirus, and escalating privileges.

Using multiple command and control frameworks in red team engagements helps to bypass antivirus and evade blue team detection. You need to choose C2 frameworks that have robust security features and advanced automation to have a successful engagement. By leveraging the strengths of different C2 frameworks, red teams can simulate complex attacks and find weaknesses in an organization's defenses, to improve overall security.

Using C2 Frameworks for Penetration Testing

C2 frameworks, or command and control frameworks, are a must-have for penetration testers to simulate real-world attacks and test the defenses of a target system. However, using these frameworks comes with legal and ethical considerations for red teams.

• Legal and Ethical Considerations: before using a C2 framework for penetration testing, make sure you have the necessary permissions and comply with all applicable laws and regulations. Unauthorized use of C2 frameworks can lead to severe legal consequences.

• Benefits of C2 Frameworks: C2 frameworks offer many benefits for penetration testers. You can manage compromised systems, automate tasks, and simulate real-world attacks. This will help you find vulnerabilities and improve the overall security posture of the target system.

• Popular C2 Frameworks: there are many C2 frameworks available, each with its strengths and weaknesses. Havoc, Cobalt Strike, and PowerShell Empire are the most popular ones. Choose the framework that suits your needs and goals.

• Advanced Automation: many C2 frameworks have advanced automation capabilities, to automate repetitive tasks and streamline your workflow. This is very useful in large-scale operations where manual intervention is not practical.

• Same Kali Linux Machine: you can manage multiple C2 frameworks from the same Kali Linux machine, so you can switch between different tools and frameworks as needed.

• Infected Machine Remotely: C2 frameworks allow you to manage compromised systems remotely, so you can do penetration testing from anywhere.

• User-Friendly Interface: many C2 frameworks have user-friendly interfaces, so it's easy to use even for less technical users.

• C2 Framework Havoc: Havoc is a popular C2 framework known for its features and tools to manage compromised systems. Its advanced automation and robust security features make it a favorite among many penetration testers.

• Manage Compromised Systems: C2 frameworks allow you to manage compromised systems efficiently, automate tasks, and simulate real-world attacks to test the defenses of a target system.

• Run Windows PowerShell Commands: many C2 frameworks support running Windows PowerShell commands on compromised systems, so you can automate tasks and do complex operations.

• Ethical Considerations When Using: always consider the ethical implications of your actions when using C2 frameworks. Make sure your activities are authorized and not causing harm or violating any laws.

• Robust Security Features: the security features of C2 frameworks will protect your compromised systems from detection and your operations from being compromised.

• Attack Systems: C2 frameworks allow you to simulate real-world attacks on target systems, find vulnerabilities, and improve defenses.

• Legitimate Network Traffic: some C2 frameworks are designed to mimic legitimate network traffic, so it's harder for defenders to detect and respond to attacks.

• Red Team Operations: C2 frameworks are used in red team operations to simulate real-world attacks and test the defenses of a target system.

• Multiple Hosts Simultaneously: many C2 frameworks support managing multiple hosts at the same time, so you can scale your operations.

• IP or Domain Name: C2 frameworks can be configured to use specific IP addresses or domain names, so you can simulate real-world attacks and test the defenses of a target system.

By knowing the benefits and ethics of C2 frameworks, pentesters can simulate attacks and harden their target systems.

Protecting Against C2 Frameworks: Legal and Ethical

So what can you do to protect your systems from command and control frameworks? Here's what:

• Network Segmentation: isolate critical systems and limit the damage if an attacker gets in.

• Intrusion Detection Systems (IDS): these will monitor traffic and flag C2-like activity.

• Regular Threat Intelligence Feeds: keep your defenses up to date with the latest intel and block known C2 infrastructure.

• Ethical Considerations When Using: addressing legal and ethical considerations when using C2 frameworks is key. Know the laws and ethics around penetration testing and hacking so you can use them responsibly.

Integration with security orchestration tools helps with operations and protection.

Legal and Ethical Considerations

While command and control frameworks are powerful, they come with legal and ethical implications. Know the laws and regulations around C2 frameworks, especially in scenarios like penetration testing, red teaming, and ethical hacking.

Make sure you have the necessary permissions and authorizations to deploy these frameworks and don't break any laws or regulations. Ethical considerations are just as important; practitioners must follow ethical guidelines to not cause harm or do unauthorized activities. Always use C2 frameworks within the bounds of the law and ethical standards.

Integration with Other Security Tools

Command and control frameworks can be made more powerful by integrating them with other security tools to improve detection and response. Here's how:

• SIEM Systems: security Information and Event Management (SIEM) systems can monitor and analyze network traffic in real time. Integrate C2 frameworks with SIEM systems and security teams will have a complete view of network activity and can detect suspicious behavior faster.

• Threat Intelligence Platforms: integrate C2 frameworks with threat intelligence platforms to get real-time threat intel. This will help identify known threats and improve overall detection and response.

• Incident Response Tools: integrate C2 frameworks with incident response tools and organizations can automate response and remediation. Once a threat is detected, appropriate actions will be taken quickly to mitigate the risk.

• Security Orchestration Tools: security orchestration tools can automate workflows and incident response. Integrate C2 frameworks with these tools and all security controls will work in harmony to protect the network.

These integrations make C2 frameworks more powerful to manage compromised systems and respond to threats.

What's Next?

As defenses get better, attackers get better too. In the future, we will see more AI-powered command and control frameworks, more encrypted communication, and more cloud-based infrastructure to evade detection. For modern Windows systems, the architecture for payload creation is x64 and the payload format should be a Windows executable file (Exe).

The future of C2 frameworks will be shaped by:

• Cloud-Based C2 Frameworks: cloud-based C2 frameworks are getting popular due to scalability and flexibility. Attackers can manage compromised systems from anywhere, making it harder for defenders to track and block them.

• AI and Machine Learning: AI and machine learning are being used to improve C2 frameworks. These technologies can improve detection and response, making C2 frameworks more adaptive and harder to detect.

• Evasion Techniques: as detection methods get better, C2 frameworks will include more sophisticated evasion techniques. This includes encryption, polymorphic code, and other methods to evade security tools.

• Red Team Operations: C2 frameworks will continue to be used in red team operations to simulate real-world attacks. This will help organizations test their defenses and improve incident response.

By being aware of these trends, security professionals can prepare for the C2 framework landscape.

Conclusion

Command and control frameworks are powerful tools to control compromised systems and networks. But they also raise legal and ethical concerns especially when used in red team operations. Use C2 frameworks responsibly and by the laws and regulations. 

By understanding the benefits and risks of C2 frameworks, organizations can improve incident response and reduce the risk of attacks. Proper management and detection of C2 framework activities will ensure compromised systems are identified and mitigated quickly and the network is secure and intact.

Ready to enhance your C2 framework detection capabilities? Book a demo to see how our threat hunting platform can help detect C2 servers, frameworks, and other malicious infrastructure, keeping your network protected.