How to Block DDOS Attacks on Linux

How to Block DDOS Attacks on Linux

How to Block DDOS Attacks on Linux

Linux is an operating system that has emerged as a prominent player in the server market, thanks to its stable nature and open source. It’s considered the most secure OS available today. But, this doesn’t mean that it’s completely secure from intrusions. Linux systems are as vulnerable as others to cyber attacks.

Blocking DDoS Attacks On Linux

1) Access Control Lists (ACL)

Suppose you want to block traffic originating from a particular IP address. You can use ACLs. The following example will block all incoming requests from the given IP address by setting up a default deny policy.

ACLs can create policies that filter traffic using IP addresses, ports, protocols, and other criteria.

2) Linux Virtual Server (IPVS)

This feature can be used to block DDoS attacks for a particular server. It forwards requests from the same client to the same backend server, increasing performance and preventing attacks. To enable this technology, you need to install an iptables extension called “ipvsadm.”

3) Load Balancing

Load balancing involves distributing the workload to different servers/computers so that each system performs at optimal levels. This prevents overloading of any one system, thereby preventing DDoS attacks and ensuring optimum performance of your network. You can use a host of tools such as LVS or Keep lived for achieving high availability and fault in distributed systems. These tools also protect against DDoS attacks and distribute incoming loads to different servers.

4) Using Linux Containers

Containers provide a lightweight alternative to full virtualization. They’re helpful when you need to deploy large numbers of applications and desktops on your system using fewer hardware resources. You can also use Dockers tools to create isolated containers that run within a shared host environment. Such tools can be used for faster deployment of web services without the overhead of heavy operating systems like CentOS, Debian or Ubuntu.

5) Implement Intrusion Detection System (IDS)

An IDS is an agent program that monitors network traffic for malicious activities to prevent DDoS attacks. This agent runs on all hosts within your network and intercepts incoming traffic to check if it contains any malicious packets.

6) Use Kernel Network Monitoring Tools

Kernel Network Monitoring tools such as ‘Netfilter and ‘ipset’ can be used for protecting against large-scale attacks. These tools allow you to set up firewalls at different levels of your network, depending on the type and origin of incoming traffic. 

For example, you can block all requests from a particular IP address or only allow access to approved resources while blocking everything else. You can also limit the number of connections that an IP address can open with the system by using such monitoring software.

Components of Linux OS

1) Kernel

The kernel is the core of any Linux-based operating system. It manages memory allocation and prioritization, along with hardware and software resources. It also acts as an interface between applications and hardware devices.

2) Libraries

Libraries are groups of reusable code that serve as the basis for applications and software.

3) Daemons

Daemons are background processes that perform various tasks and services. They’re independent of the user interface. They run in the background and don’t require any direct interaction from users.

4) Environment

The environment handles a range of tasks, starting from managing files to running processes and networking.

5) Shell

The shell provides an interface to access core Linux commands.

6) Desktop Environments

These are used to provide the graphical face of Linux systems. They define the look and feel of GUIs in Linux systems.

7) User Interface

This is the part that’s exposed to end-users and interacts with them.

Attack Types On Linux OS

1) Resource Exhaustion

This type of attack involves exploiting system resources such as CPU, memory, and disk space to the point where it crashes or slows down. This can be done by flooding the targeted system with packets or connections to use up its resources.

2) Denial of Service (DoS)

The motive behind the DoS attack is to block access to specific systems or services. For instance, attackers might flood network traffic on port 80 so that websites hosted on that server aren’t accessible.

3) Distributed DoS (DDoS)

In this attack, a large number of systems are used to target a single system. The idea behind such an attack is to exhaust that system’s resources by making multiple requests from different points on the Internet. To get a better understanding of this attack, read our article on [DDoS article here]

4) Man In The Middle (MITM)

This type of cyberattack is also known as “session hijacking.” It involves gaining access to data that’s being transferred between two systems. The purpose is to obtain sensitive information, such as usernames, passwords, credit card details, etc.

5) Botnets

A botnet is a network of zombie computers remotely controlled by attackers. These machines are infected with malware capable of launching DDoS attacks without the knowledge of their owners.

How to Defend Against DDOS Attacks?

Now that you understand the various types of cyberattacks and their motives, here are some ways to prevent them from succeeding against Linux-based servers/systems.

1) Keep Everything Updated

Attackers typically exploit vulnerabilities in outdated versions of Linux, such as kernel versions. The best way to prevent such attacks is to keep your operating system and software up to date with the latest patches and security updates. This ensures that there aren’t any loopholes for hackers to breach systems and servers remotely.

2) Use Only Trusted Software

While it’s possible to download and install open-source programs from third-party sources, this practice isn’t safe. Unofficial app stores may host pirated content that isn’t correctly vetted before making it available for download. Hence, stick to downloading content from official websites only instead of taking the risk.

3) Secure Passwords

Passwords are the first line of defense when it comes to protecting Linux systems. It’s essential to select complex and lengthy passwords that can’t be easily guessed or cracked by hackers. Use a combination of upper case, lower case letters along with numbers in your password.

Don’t make them similar to their names either. You can also use a password manager to store and generate secure passwords for each of your online accounts. These managers typically include security features, such as two-factor authentication, to enhance account security further.

4) Be Wary Of USB Drives

Many organizations have insecure policies that allow users to connect their pen drives or USBs to computers. This can potentially harm the network in several ways, such as infiltration of malware, data theft, and so on. You should implement strict guidelines for connecting USBs to your systems along with regular monitoring to ensure that no sensitive information is being leaked out.

5) Use A Dedicated Router

The modem provided by your ISP or shared within an office environment may not be secure enough to protect against DDoS attacks. The best way to prevent such attacks is to invest in a separate router for your Linux systems. This router should only allow connections from approved IP addresses and also include other security features, such as fail-safe support, to prevent your systems from potential attacks.

6) Keep Software Updated

Attackers commonly exploit vulnerabilities in the Linux kernel, which is the core component of your operating system. This is why it’s essential to keep all software up to date with the latest version that usually includes patches and security updates to plug the loophole.


Suppose a Linux server appears to be sluggish or is under constant attack. In that case, the best option is to hire a professional system admin who knows how to handle security threats and prevent DDoS attacks. You can also use free open source applications for setting up firewalls and other security features. Above all, never ignore any warning signs as this will only worsen any potential damage caused by such attacks.

Always keep your network updated, use high-quality hardware, and most importantly, ensure a regular backup of all critical data to remain protected at all times. If you feel any website is being attacked or the server is under malware attack, then just consult Linux experts for business Linux support from expert professionals and make your website safe.

Be cautious and follow all security guidelines to avoid such attacks. You can also use a free Linux anti-DDoS tool for protecting your web servers and websites from DDoS, DoS, and other malicious attacks.

Hope you found this article helpful to stop DDoS attacks on Linux.

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