Malware

What is Command and Control(C2) Server – A Detailed Overview

Like a regular system holder, you might wonder why your system is running slower than usual. Always you are getting random messages like a pop-up, something got added as an extension in your browser and you have never used this.

Your browser cannot load the page, internet connectivity is slow, and even the computer is always slow and sometimes it even crashes. We have no idea why all this is happening.

Well, the only answer is malware which is doing all such things. Your machine has been infected in a very bad way and it can only become proper by turning into a zombie which C&C controls.

Now you might be wondering what is all about C&C? Well, this full name is Command-and-control Servers. The hackers mainly use this communication with a target network by using the system. These systems may be Smartphones, Computers, LOTs, etc.

Just in the second paragraph, we have mentioned the name “zombie”, it is also called a botnet that is a combination of robot and network. This is a machine which infected with the Trojan horse, and it gets controlled by the C2C server.

This botnet is the collection of computer sets that get used without the knowledge of their owners and send files to other computers through the internet. The file includes spam and malware.

Now the question is why communication is required? Well, the answer is botnets has to follow the instruction given by C&C. The instruction has set as command-based, which is the structure of the botnet. It has been installed as a key logger which can collect sensitive information like spam emails, credit card numbers, conduct DDoS attacks, etc. The botnet cannot upload the reports or give them the result because it can only do whatever the commander (C&C) tells them.

Table of Contents

FAQ
What all are hackers can do through Command and Control?
What does the botnet architecture look like?
Botnet Architecture Types
The Overview of Infection Methods
What will you do when the computer will turn into Zombie?
Conclusion

FAQ

1. What is a C2 framework?

Attackers or cybersecurity professionals employ a C2 (Command and Control) framework to communicate and control hacked systems or networks.

These frameworks are commonly linked to network attacks, botnet management, and malware control in cybersecurity. They are legitimately used in penetration testing and security assessments to simulate assaults and find weaknesses.

C2 frameworks provide remote control, data exfiltration, and command execution on compromised machines, making them essential to the effectiveness and stealthiness of cyber operations for malevolent intent or security testing.

2.What are the common C2 protocols?

HTTP/HTTPS, DNS, ICMP, SMTP, and TCP/UDP are cybersecurity Command and Control (C2) protocols. HTTP and HTTPS are popular because they are ubiquitous and C2 traffic is hard to differentiate from typical web traffic, making them effective for evasion.

Since DNS is essential for internet functionality and can discreetly transport data in queries and responses, it is widely utilized for C2 communications. ICMP, less prevalent for C2, can transport data discreetly.

SMTP controls viruses via email. TCP and UDP are basic communication protocols used in custom C2 methods. These protocols are chosen because they blend seamlessly with network traffic, avoiding network security monitoring.

3.What is C2 over DNS?

Attackers utilize DNS to communicate with hacked computers via C2 (Command and Control).

The malware on the compromised system communicates with the attacker’s C2 server using DNS requests. DNS request and response messages hide the communication, making it less obvious than HTTP.

DNS is a fundamental and pervasive aspect of network infrastructure, therefore C2 communications can mix in with genuine DNS traffic without being banned or inspected.

Network security technologies struggle to identify and stop stealthiness. Exfiltrating stolen data, receiving orders, or downloading additional payloads can occur over DNS as normal traffic.

What all are hackers can do through Command and Control?

  1. Data theft: In this process, a company’s data which is very sensitive, like financial documents, can be copied, and those also can be transferred to the attacker’s server.
  2. Shutdown: One attacker can shut down many machines together and even make the network of the targeted company.
  3. Reboot: When the computer gets infected, it may suddenly shut down and reboot which will become a problem for any normal business operation.
  4. Distributed denial of service (DDoS): It overwhelms the server and floods them with too much internet traffic. As soon as the botnet gets established, the attacker will instruct every bot to send a request to the company’s targeted IP address. This creates an appeal with the targeted server, and the result is traffic gets clogged on the highway. It can legitimate the traffic by attacking IP addresses, and it denies access. This type of attack they do to take the website down.

This is the diagram where you can see how to stop the attacker from using DNS against you:

BotMaster

What does the botnet architecture look like? And how does it work?

While reading this article, you might be wondering why we need bots and what are their uses. Let us take an example of spamming. Here sending spam is getting blacklisted because it is already set in some specific address.

To overcome this issue, you need to send spam, but for zombies to find the unique address from thousands, it is a cupcake for it. By sending more emails, attackers can make enormous money.

botnet architecture

If you consider the fact that the C&C server is intended to conduct DDoS then Zoobies’s army keeps on sending the false request to the webserver and the webserver will not be able to handle the multiple request time they will do the leading attack on DDoS. After this criminals want money and they demand from the owner and after getting that they will stop such an attack.

It is effortless for a botnet to create a zombie army by installing software by stealing a password. These software mainly steal passwords from bank accounts, emails, credit card numbers, and criminals who sell passwords to make money. Zombie Army only deals with all illegal activity.

Botnet Architecture Types

There are two types of architecture which include centralized and decentralized or peer-to-peer. These are discussed below:

  • Centralized:
  • This is a very common type that is centralized with a C&C server, which provides the resources by individual client request. This network is completely based on the client-server model. Usually, this type of botnet gets to communicate with Internet relay chat (IRC).
  • IRC is a computer program that user can easily install in their system.
  • Through the chat server, clients can send transfer messages to the other client.
  • IRC is not so simple, and it uses the low bandwidth communication method, which makes it a broader use to host botnets.
  • They look straightforward for the construction, and they get used to getting moderate success so that they can coordinate with DDoS attacks and switch the channel so that they can avoid them.
  • Decentralized or Peer-to-Peer:
  • Desperately using centralized servers has its advantages. There is a problem with using centralized servers if that is used by IRC. Every botnet client must know about the IRC server, port, and other channels.
  • To halt the botnet attack, anti-malware organizations detect the server and make it shut down.
  • To bring down a centralized server, you have to leave the zombies dead, and the botnet army will have no work with the attackers.

The Overview of Infection Methods:

You might be wondering how C&C recruitment has been done and how to create an army for botnets. Let us inform you there are multiple ways to turn the computer into a botnet. Those are discussed below:

  1. Email: Usually, attackers send you an email with a code in an attached file, or sometimes they even send a link with malicious code. After clicking on the link will lure the attacker which drops the malware within the machine and it will turn into a Zombie.
  2. Exploiting Vulnerabilities: Many vulnerabilities get exploited, which are offered from the backdoor of the machine. This mainly gets used by the attacker who drops the malware into the machine. Vulnerabilities include browser plugins, add-ons, and other software which are already installed on the machine.

What will you do when the computer will turn into Zombie?

  • You can use some Sysinternals tools that find the process to consume more memory. If it finds any suspicious process, then you can kill that process.
  • You always need to scan the machine with a different antivirus engine to recheck whether it is getting detected or not malware. This cannot be the complete solution, but it has to identify the malware with the latest signature.
  • Maximum antivirus fails to detect and remove the malware if it’s the most advanced one. It can link by itself with the operating system and process.
  • If the rootkit is hard and cannot remove the infection then the most effective thing is to clean the machine and restore the backup. But before you start, make sure that you keep a backup of everything so that you do not lose any data.
  • After you clean the malware, you can regularly apply the security update to avoid future infection.

Conclusion

By reading this article, you have come to know how much C2 is essential for our daily life.

Just a tiny malware can do massive damage, so we have taken the help of a botnet army that can control everything and make better communication.

Guru Baran

Gurubaran is a co-founder of Cyber Security News and GBHackers On Security. He has 10+ years of experience as a Security Consultant, Editor, and Analyst in cybersecurity, technology, and communications.

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