ConfigServer Security & Firewall – front-end to iptables or nftables

Last Updated on March 4, 2026

ConfigServer Security & Firewall (CSF) is a Stateful Packet Inspection (SPI) firewall and Login/Intrusion Detection and Security application for Linux servers which started back in 2005. CSF works as a front-end to iptables or nftables, configuring your server’s firewall rules to lock down public access to services while allowing only approved connections.

This provides better security for your server while giving you an advanced, easy-to-use interface for managing firewall settings. With CSF in place, you can safely permit activities such as logging in via FTP or SSH, checking email, and loading websites, while unauthorized access attempts are blocked.

This is free and open source software.

Key Features

• Firewall & Network Security
  • Easy-to-use SPI firewall powered by iptables/nftables.
  • Pre-configured for cPanel and DirectAdmin (standard ports open by default).
  • Auto-detects non-standard SSH ports during installation.
  • Works with multiple network interfaces.
  • Supports IPv6 via ip6tables.
  • Block traffic on unused server IPs to reduce attack surface.
  • Country-based access control (allow/deny by ISO Country Code).
  • Protection against:
    • SYN floods.
    • Ping of Death.
    • Port scans.
    • Connection flooding (per IP/per port detection).
  • Permanent or temporary IP blocking (with TTL support).
  • Integration with blocklists like DShield and Spamhaus DROP.
  • BOGON packet protection.
• Login & User Monitoring:
  • Login Failure Daemon (LFD): detects repeated login failures (brute force protection).
  • Monitors authentication for:
    • SSH (OpenSSH).
    • FTP (Pure-ftpd, vsftpd, Proftpd).
    • Mail (Courier IMAP, Dovecot, Kerio, Exim SMTP AUTH, POP3/IMAP).
    • Web (cPanel/WHM, Webmail, htpasswd-protected pages).
    • ModSecurity (v1 & v2).
    • Suhosin.
    • Custom services via regex and log file matching.
  • POP3/IMAP login tracking (limit logins per hour).
  • Distributed attack detection (across multiple servers).
  • LFD clustering – share blocks/whitelists across a server group.
  • Temporary IP allows (with TTL).
• Alerts & Notifications:
  • SSH and su login notifications.
  • Root access notifications (WHM).
  • Alerts for:
    • High server load average.
    • Excessive email sending per hour (spamming detection).
    • Suspicious processes running.
    • Abnormal file activity in /tmp and similar directories.
    • Excessive user processes or resource usage.
    • Account changes (password updates, shell changes, etc.).
• Intrusion Detection & Exploit Protection:
  • Intrusion Detection System (IDS) – monitors system/application binaries.
  • Suspicious process and file reporting.
  • Exploit checks.
  • Directory and file integrity monitoring.
  • ModSecurity log reporting.
  • Messenger Service – optionally redirect blocked users to a custom page explaining why access is denied.
• Management & Control:
  • Integrated UI for major control panels:
    • cPanel, DirectAdmin, InterWorx, CWP, VestaCP, CyberPanel, Webmin.
  • cPanel reseller access (per-reseller firewall controls: Allow, Deny, Unblock, Search).
  • Integrated with CloudFlare Firewall.
  • Upgrade firewall directly from control panel or shell.
  • Quick start mode for servers with large allow/deny lists.
  • Easy Dynamic DNS support (auto-allow your changing home IP).
  • System statistics & graphs (CPU, load, memory, etc.).
  • ipset support for handling large IP lists efficiently.
  • Integrated support for cse within the UI.

Website: github.com/aetherinox/csf-firewall
Support:
Developer: Aetherinox
License: GNU General Public License v3.0

CSF is written in Perl. Learn Perl with our recommended free books and free tutorials.

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