The Command and Control Attack is a type of cyber attack in which a hacker controls an individual’s PC and uses it to inject malware into other computers connected to the same network in order to create an army of bots. The Command and Control Cyberattack is shortly abbreviated as C2 or C&C. To perform a C&C attack at an advanced level, hackers usually try to have control over the entire network through which the computers in an organization are connected to one another so that all the computers on a network can be infected to create an army of bots. In this article, we will talk about Command and Control Cyberattacks and how you can identify and prevent them.
Command and Control Cyberattack
A C2 or C&C attack includes the set of tools and techniques that hackers use to communicate with the compromised devices in order to give the instructions to spread the infection. In a Command and Control Cyberattack, one or more than one communication channel can exist between a victim’s PC or an organization and the platform that a hacker controls. The attacker uses these communication channels to transfer instructions to the compromised devices. DNS is a widely-used communication channel for a C2 attack.
Before we discuss more on Command and Control Cyberattack, there are some terms related to the C&C attack that you should know.
A Zombie is a computer or a device that has been infected by the attacker with some form of viruses or malware. After transforming a healthy computer into a zombie, the attacker can control it remotely without the knowledge or consent of its owner. In a C2 infrastructure, the malware or viruses that a hacker uses to infect a particular computer opens up a pathway for the hacker to send instructions to the infected computer. This is a bidirectional pathway, which means that the attacker can send instructions to the infected computer and also download the content from the infected computer.
The infected devices in a C2 or C&C infrastructure are referred to as zombies because these devices are used by the attacker to infect other healthy computers on a particular network. After being infected, these computers work in the same way as the zombies shown in fictional or horror Hollywood movies.
A botnet is an army of infected computers. In a C2 infrastructure, when one computer is infected, the infection is transferred to another computer connected to the network. The same process is repeated to infect other computers on the same network in order to create an army of bots. This army of bots (infected computers) is referred to as a botnet. A hacker can use a botnet for different cyberattacks, like a DDoS attack. In addition to this, a hacker can also sell botnets to other cybercriminals.
Beaconing is the process through which the malware in the infected computer communicates to the C&C server in order to receive instructions from the hacker and send data from the infected device to the hacker.
How does a Command and Control Cyber attack work?
The aim of the attacker is to get inside the target system. He can do this by installing a virus or malware on the host system. After infecting the host’s system with a virus or malware, he can have full control of it. There are many ways by which a hacker can inject malware into a user’s computer. One of the popular methods is sending a phishing email. A phishing email contains a malicious link. This malicious link can either take the user to the malicious website or tell him to install a particular software.
The software contains malicious code written by the hacker. On installing this software, malware enters his computer. This malware then starts sending data from the infected computer to the attacker without the consent of the user. This data may contain sensitive information like credit card information, passwords, etc.
In a Command and Control infrastructure, the malware in the host’s system sends a command to the host server. The transmission routes selected for this purpose are generally trusted and not monitored closely. One such example of this route is DNS. Once the malware succeeds in sending the command to the host server, the host’s computer transforms into a zombie and comes under the control of the attacker. The attacker then uses the infected computer to transmit the infection to other computers so that an army of bots or botnet is created.
Apart from stealing the user’s data, a hacker can use a botnet for various purposes, like:
- Hitting the popular websites with DDoS attacks.
- Destroying the user’s or organization’s data.
- Interrupting the organizations’ tasks by hijacking their machines.
- Distributing the malware or viruses to other healthy machines over a network.
Command and Control Servers
The Command and Control servers are the centralized machines that are capable of sending instructions or commands to the machines that are part of a botnet and receiving the output from the same. There are various topologies used in Botnet Command and Control Servers. Some of these topologies are explained below:
- Star topology: In Star topology, there is one central C&C Server. This server sends instructions or commands to the bots in a botnet. In this topology, it is comparatively easier to disable the botnet because there is only one C&C server that sends all the commands to the bots and receives the output from the same.
- Multi-server topology: This topology is similar to the Star topology that we have described above. But the central server in this topology consists of a series of interconnected servers. The Multi-server topology is considered more stable than the Star topology because the failure of a single server does not cause shut down of the entire C&C server. Building a Multi-server C&C Server topology is more complex than the Star topology as it requires setting up different servers, which needs proper planning.
- Random topology: In a random topology, some specialized bots are used to send instructions or commands to other bots over a botnet network. These specialized bots are operated by the owner or an authorized user. Such types of botnets have very high latency and are difficult to dismantle. In a Random topology, the bot-to-bot communication can be encrypted making it a more complex C&C Server topology.
How to identify the Command and Control Cyberattack
You can identify the Command and Control Cyberattack with the help of log files.
- DNS log files: As described above, DNS is the most commonly used communication channel in Command and Control Cyberattacks. Hence, the DNS log files can provide you with crucial information regarding the C&C attacks. As we have said, most C&C attacks are made through the DNS servers. But if the C&C attack is not made through the DNS server, the DNS log files will not give you any information about the attack.
- Proxy log files: Most organizations use filtering proxy. The user’s traffic has to go through this proxy for security reasons. The log files of web proxy can be a crucial source of information regarding the Command and Control Cyberattack.
- Firewall logs: Firewall logs can also be a good source for a C&C attack investigation.
After collecting the information from various log files, you can look for the following information in the log files to confirm whether a C&C attack has taken place.
- The repeating pattern of HTTP requests,
- Connections to the HTTP servers especially outside the regular office hours,
- Request to the social networking sites, especially outside the regular office hours,
- DNS responses with a low TTL,
- Repeated requests for the URL shortener domains,
- Outbound IRC or P2P traffic, etc.
How to prevent the Command and Control Cyberattacks
Now, let’s talk about some ways by which you can prevent the Command and Control Cyberattacks.
Security tips for organizations or administrators
First, see the ways by which the organizations or system administrators can prevent the Command and Control Cyberattacks.
Awareness among the employees
The first thing that organizations should do is to provide awareness training to all employees so that they could know what a Command and Control attack is and how it can be done. This will minimize the possibility of a system being hacked by an attacker. By providing appropriate training to your employees, you can lower the risk of a C&C attack.
Keep an eye on your network
In most cases, the Command and Control Cyberattacks are done over a network. Therefore, it is necessary to monitor the flow of traffic over your network. While monitoring your network, you have to look out for suspicious activities being done on your network, like:
- Accessing unusual network locations,
- User logins outside the office hours,
- Files are being stored in odd locations, etc.
Set up two-factor authentication on all your employees’ accounts
The two-factor authentication adds an additional security layer. Hence, it is a great way of securing your user accounts. However, attackers can also bypass the two-factor authentication, but it is not as easy as it sounds.
Limit user permissions
Limiting user permissions can be a good step to secure your systems from the Command and Control Cyberattacks. Assign your employees only the permissions required by them to do their work and not more than that.
Security tips for users
Let’s see some security tips for the users to prevent the Command and Control Cyberattacks.
Do not click on the untrusted links
We have described earlier in this article that attackers can enter into the host’s computer in many ways. One of these ways is the phishing emails that contain malicious links. Once you click on these links, you will be redirected to a malicious website, or malware is downloaded and installed on your system automatically. Hence, to be on the safer side, never click on the links that are from the untrusted emails.
Do not open the attachments from untrusted emails
Do not open the email attachments unless you know who the sender is. Some email clients, like Gmail, have an email attachment scanning feature. But sometimes this feature does not work on some particular email attachments. In such a case, if you do not know the sender of the email, it will be better not to open such emails.
Log out every time you finish your work
Logging out from all accounts after finishing work on a computer is a good practice to prevent all types of cyberattacks. Also, you can set your browser, like Firefox, Chrome, Edge, etc., to clear cookies automatically on exit.
Install a firewall or a good antivirus
Always install a good antivirus on your system. Some antiviruses also offer an email scanning feature. It will be best if you have a budget to purchase a complete security suite that offers various features like email scanning, data breach alert, ransomware protection, webcam protection, etc. You can also install a good firewall.
Create strong passwords
It is always recommended to create strong passwords. Passwords are case-sensitive. Therefore, create a password with a combination of special characters, small and capital letters, and numerals. You can also use free password generators to generate strong and unique passwords.
Keep your system up to date
Keeping a system up to date is recommended because with every update, the developer release the latest security patches. These security patches help protect your system from cyber threats.
What are some indicators of a cyberattack?
Following are some symptoms that your system will show if it is compromised.
- You will not be able to access usual files or applications.
- Some of your system settings are blocked.
- Your account has been locked or its password has been changed without your knowledge.
- You will see unwanted popups in your web browser most frequently.
- You will experience slower internet speeds without congestion in your internet network.
- Programs installed on your system will get launched and closed automatically.
How can you prevent cyber threats?
To prevent cyber threats, you can do some needful things, like signing out of all your accounts every time you finish your work, clearing your web browser cookies on exit, installing a good antivirus and firewall, creating strong passwords, etc.
Read next: What is Session Hijacking and How To Prevent It.