What is Command and Control Attacks?

A Command and Control (C&C) attack involves using tools to communicate with and control an infected machine or network. To maximize profit from a malware attack, a hacker needs a covert channel or backdoor between their server and the compromised network or machine. The server controlled by cybercriminals, whether a single machine or a botnet of machines, is known as the command-and-control server (C&C) or C2 server.

The number of malware programs exceeds one billion, with over 300,000 new ones discovered daily. This increasing threat of cyberattacks is not only a concern for governments and large corporations; 80% of malware attacks target small and midsize businesses (SMBs).

For cybercriminals, a successful attack goes beyond unauthorized entry or malware installation. To profit from stolen data, a hacker typically needs to remain undetected within the system or network. To achieve this, they use a command-and-control (C&C) server. C2 servers mimic trusted or unmonitored traffic to avoid detection for as long as possible. The established backdoor channel becomes a means to take control of the victim’s computer or network for criminal activities, such as data exfiltration, using computers for cryptocurrency mining, or shutting down entire networks.

How Do Command-and-Control Attacks Work?

To execute a command-and-control attack, the perpetrator initially infects the targeted machine or network with malware using specific cyberattack methods like phishing, social engineering, or malvertising.

Once a computer or device is infected, it becomes a “zombie,” and the malware establishes communication with the C2 server to signal readiness to receive commands from the controlling server. Through this established connection, the malicious host can deploy additional harmful software, extract data, and propagate the infection to other network resources. If successful in compromising entire sections of the network, the command-and-control server essentially governs a botnet of infected machines.

So, what exactly is C&C? It serves as the central point of a communication system that hackers employ to manipulate their victims’ computers.

Most Vulnerable Devices for C2 Attacks

While many organizations have defenses against external attacks, hackers face the challenge of locating a vulnerable computer or network for infection. Once access to the system is gained, internal network security defenses are typically weaker. Therefore, although the initially infected device may not be the primary target, it serves as the gateway into the system. Hackers may target various devices, including:

• Edge devices like routers and switches
• Internet-of-Things (IoT) devices such as handheld scanners
• Laptops
• Smartphones
• Tablets

Server Architecture Used in C2 Attacks

There isn’t a singular architecture for C&C attacks, but hackers employ specific models.

Centralized

In the centralized model, the setup resembles a traditional client-server model. The malware on the infected device(s) acts as the client, regularly or randomly contacting the server for instructions. This architecture is relatively easier to detect and remove due to its single-source IP address. To avoid detection, hackers must develop more complex servers, employing tactics like load balancers, redirectors, and other defensive measures. Additionally, they often utilize well-known websites and public cloud services to host their servers.

Peer-to-Peer (P2P)

P2P functions as a decentralized server, lacking a master or centralized module, typically using a botnet. While harder to detect, it presents challenges for the attacker in providing instructions to the entire botnet. One tactic employed by malicious actors is setting up a centralized C2 server alongside a P2P server model as a backup in case the centralized C2 is discovered and removed.

Random

The random C2 architecture is the most difficult to detect and block. Commands originate from various random sources such as content delivery networks (CDNs), emails, social media images, comments, etc. The peril lies in these sources being both random and generally trusted, unblocked, and unsuspected.

Dangers of and Potential Damages from C2 Attacks

Regardless of the chosen model, a malware infection establishing a command-and-control channel can lead to various costly consequences for an organization. While some attacks may initially affect only one machine or part of the network, others can proliferate extensively before being detected. Below are some of the dangers and damages associated with C2 attacks:

Data Theft

The C&C channel can be utilized to extract and transfer data to the C2 server, including sensitive company or client information, financial documents, proprietary assets, and other valuable data that can be exploited or sold.

Disruption

Frequent, unpredictable shutdowns initiated by infected machines can disrupt operations and necessitate redundant efforts by personnel. The costs associated with downtime and reduced productivity can be challenging to quantify but certainly impact the organization’s financial performance.

Malware/Ransomware

A single malware infection within the network can propagate into multiple infections. Moreover, the compromised network may be vulnerable to other forms of attacks, such as ransomware, which encrypts data or accounts and demands payment (in money, cryptocurrency, or sensitive information) to restore access.

System Shutdown

The perpetrator controlling the network resources could initiate a complete system shutdown or extort the organization to prevent such action. The costs incurred could be direct financial losses or result from downtime and resource depletion.

Distributed Denial-of-Service (DDoS) Attacks

If the infection spreads across the network, the compromised machines can be used to form a botnet under the control of malicious entities. This poses a risk of spreading threats to other organizational resources or even other entities, as botnets are commonly employed in DDoS attacks aimed at overwhelming servers or networks with excessive traffic to disrupt or render them inaccessible.

How To Detect C&C Traffic

To remain vigilant and identify C&C activity, your organization can implement the following measures:

• Monitor Data Traffic: Keeping an eye on data traffic is essential, albeit labor-intensive and time-consuming. While analyzing all data traffic may not be feasible, watch out for unusually large data exchanges or unauthorized traffic as part of your data security strategy.
• Log and Review DNS Inquiries: Since C2 channels often camouflage themselves within legitimate Domain Name System (DNS) traffic, examining DNS inquiries for anomalies can help uncover malicious activity.
• Identify Abnormalities: Any abnormalities in network traffic could indicate either an infected machine or malicious actions by malware.
• Monitor Encryption Usage: Malware frequently employs encryption to mask data exfiltration. Implement checks to monitor unauthorized encryption usage in network traffic, as this could reveal a C&C attack.
• Implement Blacklisting: By boycotting known malicious hosts, you can prevent internal devices from inadvertently communicating with them. While this measure won’t offer complete protection against all C&C activity, it serves as a valuable security layer.

FAQ’s

How does a Command-and-Control (C&C) attack function?

A C&C attack involves utilizing tools to establish communication and control over an infected machine or network. This is typically achieved by creating a covert channel or backdoor between the hacker’s server and the compromised system.

What makes small and midsize businesses (SMBs) vulnerable to C&C attacks?

SMBs are often targeted because they may lack robust cybersecurity measures compared to larger corporations or governments. Additionally, cybercriminals perceive them as easier targets for infiltrating networks and extracting valuable data.

Can you provide examples of devices targeted in C&C attacks?

Certainly. Devices commonly targeted in C&C attacks include edge devices like routers and switches, Internet-of-Things (IoT) devices such as handheld scanners, laptops, smartphones, and tablets.

How do hackers establish control over infected machines in a C&C attack?

Once a machine is infected, it becomes a “zombie” and establishes communication with the C&C server. The hacker can then send commands to the infected machines, allowing them to deploy additional malware, extract data, or spread the infection further.

What are the different server architectures used in C&C attacks?

There are several server architectures utilized in C&C attacks, including centralized, peer-to-peer (P2P), and random architectures. Each has its own characteristics and challenges for both attackers and defenders.

What are the potential damages caused by C&C attacks?

C&C attacks can result in various damages, including data theft, disruption of operations, propagation of malware or ransomware, system shutdowns, and even participation in distributed denial-of-service (DDoS) attacks.

How can organizations detect C&C activity within their networks?

Organizations can employ various measures to detect C&C activity, such as monitoring data traffic, logging and reviewing DNS inquiries, identifying abnormalities in network traffic, monitoring encryption usage, and implementing blacklisting of known malicious hosts. These methods help organizations remain vigilant and respond effectively to potential threats.

Conclusion

C&C attacks are a serious threat in today’s digital world. Organizations must stay vigilant, understand attack methods, and invest in robust cybersecurity measures. By prioritizing detection, employee training, and proactive defenses, businesses can protect against these evolving threats and maintain trust in the digital landscape.