Command and Control Servers – why do they need to be blocked?

Command and Control (C&C) servers are a critical component of many cyberattacks. They are used by hackers to remotely control the infected devices and launch coordinated attacks. In this post, we will discuss the importance of blocking C&C servers and the risks they pose to individuals and organizations.

The C&C setup involves a central server and one or more client devices (mobile phone, computer, smart bulb, router, etc.). The controlled device, or the slave, has a light program that is designed to receive commands/instructions from the C&C server and then executes those on the local device. This setup can be utilized for many positive automation tasks. But, when this same C&C setup is used by malicious actors, it could cause a lot of damage and loss to the attacked party.
It all starts with the malicious actor setting up a server and creating a client program. The client is designed, once installed on any system, to reach back to the server and wait for further commands from the server. Some clients are also designed to spread to other devices in the attacked network, thus creating a botnet army network of infected devices.

Some of the ways the hacker might use to spread malicious code could be through SMS or email-based phishing messages, malware, trojans, security holes in browsers or firewalls, etc. Once the client-server communication has been established, the C&C server can then send commands to the client, which then executes them. Some of the activities that a C&C server will try to accomplish through the client are to steal information/data, encrypt the data (Ransomware), disrupt and/or shut down the attacked device/network, or even launch a distributed denial of service (DDoS) attack on another network.

One common method used by hackers to infect devices with malware and establish a C&C server connection is through phishing scams. This is where a hacker sends an email or message containing a malicious link or attachment, which, when clicked on, installs malware on the device. This malware then establishes a connection to the hacker’s C&C server, allowing them to remotely control the infected device. It is important for individuals and organizations to be aware of these types of scams and to be cautious when clicking on links or downloading files from unknown sources. Additionally, organizations should implement security awareness training for their employees to educate them about the dangers of phishing scams and other cyber threats.

One of the biggest, most disruptive attacks launched and caused by C&C was the Mirai botnet attack in 2016. Mirai malware was spread to a vast number of IoT devices. It was able to install on devices that had the default username and password, and then it waited for the C&C server to provide further instructions, thus forming a botnet army. The Mirai C&C then sent commands to the botnet to send out millions of DNS queries for popular ecommerce and other sites, thus making it impossible for the attacked website to respond to genuine customer traffic. This DDoS attack brought down the domain registration service provider Dyn and popular sites like Netflix and Twitter in October of 2016.

To prevent falling victim to a C&C server attack, there are several steps that individuals and organizations can take. Firstly, it is important to keep all software and devices updated to ensure that any known vulnerabilities are patched. Secondly, users should be vigilant when it comes to clicking on links or downloading and opening files received from unknown sources. It is also a good idea to subscribe to network-based cybersecurity protection offered by your internet service provider. Additionally, to protect against attacks, organizations should invest in cybersecurity solutions, such as firewalls and intrusion detection systems, security awareness training, and regular security assessments.

In conclusion, C&C servers are a critical component of many cyberattacks and pose a significant risk to individuals and organizations. By understanding the risks and taking steps to protect themselves, individuals and organizations can reduce the likelihood of falling victim to a C&C server-directed cyberattack.

To get a better understanding of the importance of network-based cybersecurity protection offerings from mobile network operators and other communications service providers (CSPs), Allot partnered with Coleman Parkes research on an independent study. 7700 smartphone users from 7 countries were surveyed and the results were enlightening.

Join our webinar on February 15th! “How Can Security Improve Telco Business Results?” – Learn the results of the exclusive independent research presented by Coleman Parkes and our colleagues at Allot.