Mitigating DDoS Attacks Using CSF: A Comprehensive Guide Print

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Mitigating DDoS Attacks Using CSF: A Comprehensive Guide

In the ever-evolving landscape of online security, Distributed Denial of Service (DDoS) attacks pose a significant threat to web hosting and domain registration services. As the CEO & Director of DOMAIN REGISTRATION INDIA PRIVATE LIMITED, with over 17 years of experience in Linux environments and control panel software, I understand the importance of implementing robust measures to protect against such threats. In this article, we will delve into the steps to control DDoS attacks using ConfigServer Security & Firewall (CSF), a powerful tool in the arsenal of web hosting professionals.

1. Installing CSF

Before embarking on DDoS mitigation, ensure that CSF is installed on your server. Utilize package management tools like yum or apt to install this essential security tool.

# For CentOS/RHEL
yum install csf
# For Debian/Ubuntu
apt-get install csf
For a detailed guide on installing, managing, optimizing, and securing CSF, please refer to our comprehensive guide here: Installing and Optimizing CSF: A Comprehensive Guide.

2. Configuring CSF Settings

Open the CSF configuration file (usually found at /etc/csf/csf.conf) and make adjustments to key parameters. Fine-tune settings such as LF_TRIGGER to expedite blocking and LF_SELECT_INTERVAL to reduce server load during attacks.



3. SYN Flood Protection

Enable SYN flood protection within CSF to counter TCP SYN flood attacks effectively. This involves setting the SYNFLOOD parameter to 1 in the CSF configuration.


Caution: Activate this option ONLY when certain of a SYN flood attack, as it will decelerate the establishment of new connections from any IP address to the server if activated.

4. Connection Tracking

Leverage connection tracking in CSF to limit the number of connections per IP address. Adjust parameters like CT_LIMIT and CT_INTERVAL to maintain control during potential DDoS incidents.

CT_LIMIT = "100"

5. Rate Limiting

Implement rate limiting to control incoming connections, especially on critical ports. Utilize the PORTFLOOD setting in CSF to define limits and intervals for specific ports.

PORTFLOOD = "80;tcp;25;5"

6. Additional Key Settings

Below are some additional recommended CSF settings to enhance DDoS protection:

LF_SSHD = "10" # Number of failed SSH login attempts before blocking
LF_SSHD_PERM = "1" # Permanent block for failed SSH attempts
SYNFLOOD_RATE = "100/s" # SYN packets per second
SYNFLOOD_BURST = "150" # Burst rate for SYN packets
CONNLIMIT = "22;5,80;20,443;20" # Connection limits for specified ports
SYNFLOOD_LOG = "1" # Enable logging for SYN flood
CT_INTERVAL = "30" # Connection tracking interval


Monitoring and Maintenance

Regularly update CSF and monitor logs for any unusual activity. In complex scenarios, refer to CSF documentation or involve your server administrator for detailed assistance.


By implementing these measures, you fortify your infrastructure against DDoS threats, showcasing a commitment to security and the seamless operation of your domain registration and web hosting services.

For further assistance, consult our detailed knowledge base at or submit a ticket at for comprehensive support tailored to your specific needs.


This comprehensive guide aims to provide you with a robust framework for mitigating DDoS attacks using CSF. By following these steps, you can enhance the security and reliability of your web hosting services, ensuring a safe and smooth experience for your clients.

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