How does a Linux cloud server use iptables to prevent a large number of concurrent connections in a short period of time?

iptables is a firewall software running on the Linux operating system. Linux distributions such as CentOS and Ubuntu can use iptables.

Step 1: Install tables

Most Linux operating systems have iptables installed by default. You can use the following command to verify whether iptables is installed:

which iptables

If a path similar to /sbin/iptables is returned, iptables has been installed successfully. If there is no return, please execute the following command to install.

CentOS operating system:

yum install iptables

Debian/Ubuntu operating system:

apt-get install iptables iptables-persistent

Step 2: Create iptables rules

Check the eth0 interface and port 80 Incoming connections:

iptables -I INPUT -p tcp --dport 80 -i eth0 -m state --state NEW -m recent --set

If there are more than 10 new incoming connections within 60 seconds, discard:

iptables -I INPUT -p tcp --dport 80 -i eth0 -m state --state NEW -m recent --update --seconds 60 --hitcount 10 -j DROP

Step 3: Save iptables rules

Create iptables After the rules, we need to save and load iptables to make the rules permanent.

service iptables-persistent save
service iptables-persistent reload

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