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How to Prevent DDOS Attack on Linux Server

A DDoS attack on Linux server is a big problem for online systems. They can make websites and services stop working, causing trouble and money loss. Linux servers, which are used a lot on the internet, are often the main targets for these attacks. In this guide, we’ll talk about different ways to make your Linux server stronger and protect it from DDoS attacks.

What Is a DDoS Attack?

A DDoS (Distributed Denial of Service) is a type of cyberattack that tries to make a network, service, or server stop working by sending a huge amount of fake traffic. This flood of messages, connection requests, or packets is way more than the system can handle, and it makes the targeted infrastructure slow down or even crash.

Some hackers resort to DDoS attacks for various reasons, not limited to blackmail for ransom, similar to how ransomware works. The more common motives behind DDoS attacks include:

1. Disrupting Services or Communications: Overloading a system with fake traffic to make it difficult or impossible for normal users to access services.

2. Inflicting Brand Damage: Intentionally tarnishing the reputation of a business or organization by disrupting its online presence.

3. Gaining Business Advantage: Capitalizing on a competitor’s downtime to gain a competitive edge, especially in industries where online presence is crucial.

4. Distracting Incident Response Teams: Diverting attention away from other security incidents or vulnerabilities by causing chaos with a DDoS attack.

Whom Do DDos Attackers Target?

DDoS attacks pose a threat to businesses of all sizes, ranging from large Fortune 500 companies to small e-retailers. Statistically, DDoS hackers most frequently target:

1. Online Retailers: Disrupting e-commerce platforms to cause financial losses and harm the brand’s image.

2. IT Service Providers: Targeting companies that offer crucial IT services, affecting their ability to serve clients.

3. Financial and Fintech Companies: Disrupting financial transactions and services, causing potential monetary losses and damaging trust.

4. Government Entities: Impeding government operations by overwhelming online systems and communications.

5. Online Gaming and Gambling Companies:

Affecting the availability of online gaming platforms and gambling websites for various motives.

Attackers typically use a botnet to execute a DDoS attack on Linux server. A botnet is a network of malware-infected computers, mobile devices, and IoT gadgets controlled by the attacker. These “zombie” devices are used to flood a target website or server with an excessive number of requests.

According to a Radware report, the average lengths of DDoS attacks are as follows:

  • 33% of attacks keep services unavailable for an hour.
  • 60% of attacks last less than a full day.
  • 15% of attacks last for a month.

Although a DDoS attack typically does not directly result in a data breach or leakage, it demands considerable time and financial resources to restore services. Consequences may include loss of business, abandoned shopping carts, frustrated users, and reputational harm for those who fail to prevent DDoS attacks effectively.

How to Prevent DDOS Attack on Linux Server

Follow the points listed below to prevent DDOS attack on Linux Server:

Strengthening Network Infrastructure

Use Firewalls:

  • Utilize iptables or firewalld to set up robust firewall rules.
  • Employ stateful inspection to monitor and control incoming and outgoing traffic.

Network Security Measures:

  • Enable anti-spoofing mechanisms to prevent the use of fake source IP addresses.
  • Utilize Virtual LANs (VLANs) to segment and isolate network traffic.

Load Balancers:

  • Distribute incoming traffic across multiple servers using load balancers.
  • Employ load balancing algorithms that can detect and mitigate DDoS attacks.

Protecting Against Volumetric Attacks

Content Delivery Networks (CDNs):

  • Integrate with a CDN to distribute content geographically, reducing the impact of volumetric attacks.
  • CDN providers often have DDoS mitigation services built into their infrastructure.

Traffic Filtering:

  • Deploy rate limiting to control the rate of incoming requests.
  • Implement tools like mod_evasive or fail2ban to identify and block suspicious traffic patterns.

Anycast DNS:

  • Distribute DNS resolution requests across multiple servers using Anycast DNS.
  • This can help absorb DDoS traffic by spreading it across multiple locations.

Mitigating Protocol-Based Attacks

SYN/ACK Flood Protection:

  • Configure TCP SYN cookies to prevent SYN/ACK flood attacks.
  • Adjust the maximum number of allowed concurrent connections to mitigate resource exhaustion.

IP Spoofing Protection:

  • Implement anti-spoofing measures at both the network and application layers.
  • Utilize tools like Source Address Validation Improvement (SAVI) to detect and block spoofed packets.

Rate Limiting and Connection Throttling:

  • Set up rate limiting for specific protocols to restrict the number of requests from a single IP address.
  • Employ connection throttling to limit the number of connections a single IP can establish.

Safeguarding Against Application-Layer Attacks

Web Application Firewalls (WAF):

  • Integrate WAFs to filter and monitor HTTP traffic.
  • Customize WAF rules to protect against common application-layer attacks like SQL injection and Cross-Site Scripting (XSS).

Intrusion Prevention Systems (IPS):

  • Deploy IPS to detect and block malicious activities at the application layer.
  • Regularly update IPS signatures to stay protected against emerging threats.

HTTP and HTTPS Hardening:

  • Disable unnecessary HTTP methods.
  • Enable HTTPS and enforce the use of secure communication protocols.

Continuous Monitoring and Incident Response

Logging and Monitoring:

  • Implement centralized logging to track system and network activities.
  • Utilize intrusion detection systems to identify and respond to suspicious behavior.

Incident Response Plan:

  • Develop a robust incident response plan to address DDoS attacks promptly.
  • Conduct regular simulations and drills to ensure the effectiveness of the response plan.

Collaboration with ISPs and DDoS Mitigation Services:

  • Establish relationships with Internet Service Providers (ISPs) for early detection and mitigation of DDoS attacks.
  • Consider employing third-party DDoS mitigation services for additional protection.


To prevent DDOS attack on Linux server, it’s important to use a variety of methods. This includes making your network strong, filtering out unwanted traffic, and always keeping an eye on things. By following the steps mentioned in this guide, you can make your server much tougher and reduce the harm from possible DDoS attacks. It’s crucial to stay watchful, regularly update your defences, and work together with others in the industry to be ahead in the constant fight against DDoS attacks.