Command and Control: Understanding & Defending Against C2 Attacks

Attackers go through several stages to make an attack successful. And the last line in the defense system they aim to break is the command and control (C2). 

C2 attacks are a severe threat to organizations of all sizes and types because, if successful, adversaries can steal all your valuable data. To protect against these attacks, you should implement a security framework and robust policies, including technical and organizational measures. 

In this article, you'll learn how command and control contribute to the security of your overall organization. 

What is command and control (C2) in cybersecurity?

The security department in organizations uses a command-and-control system to monitor its security network, identify and respond to potential threats, and communicate with its team. NIST defines C2 as:

“…the exercise of authority and direction by a properly designated commander over assigned and attached forces in the accomplishment of the mission. Command and control functions are performed through an arrangement of personnel, equipment, communications, facilities, and procedures employed by a commander in planning, directing, coordinating, and controlling forces and operations in the accomplishment of the mission.”

Some adversaries constantly seek ways to disrupt the C2 system, gain network access and steal valuable data. To achieve this, they use various techniques and MITRE ATT&CK's research highlights 16 ways attackers may compromise your C2 system:

1. Application Layer Protocol (T1071)

9. Multi-stage Channels (T1104)

2. Communication Through Removable Media (T1092)

10. Non-application Layer Protocol (T1095)

3. Data Encoding (T1132 )

11. Non-standard Port (T1571)

4. Data Obfuscation (T1001)

12. Protocol Tunneling (T1572)

5. Dynamic Resolution (T1568)

13. Proxy (T1090)

6. Encrypted Channel (T1573)

14. Remote Access Software (T1219)

7. Fallback Channels (T1008)

15. Traffic Signaling (T1205)

8. Ingress Tool Transfer (T1105)

16. Web Service (T1102)

MITRE-mapped techniques attackers can use in C2 attacks.

Once an adversary has compromised the C2 system, they can trigger the download of additional malware, steal sensitive company data such as financial documents and passwords and even bring down your company's entire network. 

Suppose you don't have strong command and control. In that case, your organization can suffer severe consequences like financial loss, reputational damage and potential legal repercussions. To prevent these attacks, your security teams must take a proactive approach to cybersecurity and implement robust command and control. You can do this using a few best practices such as: 

  • Keeping software up to date.
  • Implementing strong access controls. 
  • Using encryption.
  • Monitoring the network for unusual activity.

Pro Tip: You can use advanced technologies like AI and ML to identify and respond to threats in real time. 

How C2 attacks work

A C2 attack is a cyberattack that allows an attacker to take control of a compromised machine and use it to carry out malicious activities. 

In this attack, the attacker creates a communication channel between the infected machine and a command and control server. The communication channel then transmits instructions and data to the infected machine. Here's how a C2 attack is executed: 

  1. The adversaries will establish their foot in the targeted machine to initiate their attack. They can achieve this by phishing emails, social engineering, or exploiting vulnerabilities in software or operating systems. 
  2. Once they have access to the targeted machine, they will attempt to install malware or other malicious software that will allow them to gain control over the machine.
  3. The attackers will now build a communication line between the infected machine and the command and control server. They might use a Remote Access Trojan (RAT), a type of malware that lets you remotely control a compromised machine.
  4. Once the communication channel is built, the infected machine will signal the attacker's server to initiate malicious activity. 

This is how attackers can steal any essential data. They use this communication channel to pull out data from the compromised machine or to issue commands to carry out further malicious activities, such as launching a distributed denial-of-service (DDoS) attack.

Example of a command-and-control attack: Log4j

According to U.S. CISA Director Jen Easterly, Log4j is the most serious vulnerability, occurring early in the attack lifecycle. It's an example of how attackers can exploit vulnerabilities to make a c2 attack successful. 

Attackers can leverage it to compromise an end host, download a secondary payload and hack the entire command and control system. Once an attacker gains access, they use Log4j to escalate their privileges and gain control of the whole network. Here's how they accomplish their attack:

  • They exploit the Log4j vulnerability to access a target system and install a backdoor or malicious software. 
  • Next, they use this foothold to establish a c2 connection with the compromised system.  
  • Then, they can remotely control it and carry out further attacks.

By monitoring and detecting C2 activities, security teams or commanders can prevent attackers from establishing a foothold in their systems and carrying out further attacks.

(See how Splunk handled the Log4j vulnerability.)

Preventing command-and-control attacks 

Preventing C2 attacks requires a multi-layered approach that includes technical and organizational measures. Technical measures may include using firewalls, intrusion detection and prevention systems and endpoint protection solutions to monitor and block suspicious activities. 

Organizational measures include implementing strong access controls, such as two-factor authentication, to prevent unauthorized access to sensitive systems and data.

Security commanders can protect your organization from command-and-control attacks. Since they know C2 systems, they can identify and mitigate potential threats and vulnerabilities using their knowledge and expertise. Here's how they can thwart c2 attacks:

Monitor network traffic

Security command teams monitor the network traffic to detect any suspicious activity. By doing so, they identify and respond to any suspicious activity, preventing command and control attacks from succeeding. They use intrusion detection systems (IDS) and intrusion prevention systems (IPS), which can analyze network traffic in real-time and alert security teams to potential threats. 

(Read more about networking security monitoring & network security.)

Prioritize security implementations

Done right, prioritizing security implementations such as two-factor authentication and digital code signing can reduce the risk of command and control attacks:

  • Two-factor authentication is an additional layer of security to protect a system. To enable this, users provide a second form of identification, like a fingerprint or a code sent to their phone. 
  • Digital code signing is used to verify the authenticity of software code and ensure that unauthorized parties have not modified it.

(See what generative AIs, like ChatGPT, mean for cybersecurity.)

Provide security training to staff

Staff members must be aware of the potential risks associated with command and control attacks to contribute their part when it comes to the safety of the organization. So, the security team should educate them on the importance of strong passwords, recognizing phishing scams and avoiding suspicious websites and downloads to protect against cyberattacks. 

The best way your organization can ensure the staff is knowledgeable is by starting ongoing training about keeping up with the latest threats and learning mitigation strategies.

Protect your business from C2 attacks

Cybercriminals have become increasingly sophisticated in their approach to command and control (C2) attacks, which is a threat to organizations. By making these attacks, they can steal valuable data and compromise your organization's sensitive information. 

So, your organization should adopt a comprehensive security strategy to prevent C2 attacks. By implementing this, you can safeguard your assets, protect customers' data and maintain the trust of customers.

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This posting does not necessarily represent Splunk's position, strategies or opinion.

Laiba Siddiqui
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Laiba Siddiqui

Laiba Siddiqui is a technical writer who specializes in writing for SaaS companies. You can connect with her on LinkedIn and at contentbylaibams@gmail.com.