TCP Syn Flood Hardening – Kernel IPv4 Settings

With the increasing TCP flood attacks and AI bot scraping floods, here are some optimizations that should be added to the end of your /etc/sysctl.conf file:

# Hardening
net.ipv4.conf.all.rp_filter=1
net.ipv4.conf.default.rp_filter=1
net.ipv4.conf.all.send_redirects=0
net.ipv4.conf.default.send_redirects=0
net.ipv4.tcp_max_syn_backlog=2048
net.ipv4.tcp_synack_retries=2
net.ipv4.conf.all.accept_redirects=0

Reboot for the settings to take effect.

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Tags: .net, ai, bots, flood, floods, IPv4, kernel, optimizations, scraping, syn, sysconfig, sysctl, sysctl.conf, tcp

This entry was posted on Wednesday, January 28th, 2026 at 11:24 am and is filed under CentOS, Linux, Red Hat, Rocky Linux, Ubuntu Linux. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

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