How to use a network firewall to protect your CentOS server’s network security

How to use a network firewall to protect the network security of CentOS servers

Network security is one of the most important issues in today's Internet era. Securing a server's network security is a challenge that every system administrator must face. CentOS is a popular open source Linux operating system with powerful security features and flexible configuration options. In this article, we will explore how to use a network firewall to secure your CentOS server network and provide some code examples.

1. What is a network firewall?

A network firewall is a security device or software that sits between the server and the external network and is used to monitor and control inbound and outbound network traffic. By defining and enforcing policies to control the flow of packets, firewalls can reduce network attacks and unauthorized access. Setting up a network firewall on a CentOS server is the top priority in protecting server security.

2. Firewall configuration on CentOS server

CentOS uses firewalld as its default firewall manager. Below are some common commands and code examples to configure and manage firewalld.

1. Check the firewall status:

sudo systemctl status firewalld

2. Start the firewall:

sudo systemctl start firewalld

3. Stop the firewall:

sudo systemctl stop firewalld

4. Permanently disable the firewall:

sudo systemctl disable firewalld

5. Set the firewall to start automatically at boot:

sudo systemctl enable firewalld

6. View the firewall rules:

sudo firewall-cmd --list-all

3. Configuring firewall rules

Configuring the firewall rules of the CentOS server is the key to protecting the security of the server. The following are some common firewall rule configuration examples:

1. Allow access to specific ports:

sudo firewall-cmd --add-port=80/tcp --permanent   # 允许访问80端口
sudo firewall-cmd --reload                        # 重载防火墙规则

2. Allow access to specific IP addresses:

sudo firewall-cmd --add-source=192.168.1.100 --permanent   # 允许IP地址为192.168.1.100的主机访问
sudo firewall-cmd --reload                                 # 重载防火墙规则

3. Allow access to specific subnets:

sudo firewall-cmd --add-source=192.168.1.0/24 --permanent   # 允许子网为192.168.1.0/24的主机访问
sudo firewall-cmd --reload                                  # 重载防火墙规则

4. Allow access to specific services:

sudo firewall-cmd --add-service=http --permanent   # 允许访问HTTP服务
sudo firewall-cmd --reload                          # 重载防火墙规则

5. Allow specific protocols Access:

sudo firewall-cmd --add-protocol=icmp --permanent   # 允许访问ICMP协议
sudo firewall-cmd --reload                          # 重载防火墙规则

4. Other firewall management commands

In addition to the above examples, the following are some other commonly used commands for managing CentOS server firewalls:

1. Turn off and disable the firewall:

sudo systemctl stop firewalld        # 关闭防火墙
sudo systemctl disable firewalld     # 禁用防火墙

2. Turn on and enable the firewall:

sudo systemctl start firewalld       # 打开防火墙
sudo systemctl enable firewalld      # 启用防火墙

3. Add and delete firewall rules:

sudo firewall-cmd --add-rule=...     # 添加规则
sudo firewall-cmd --remove-rule=...  # 删除规则

4. Update firewall rules:

sudo firewall-cmd --reload            # 更新防火墙规则

5. Summary

Protecting the network security of CentOS servers is an important task. By using a network firewall, we can control network access to the server and reduce potential security threats. This article explains how to use the firewalld manager to secure a CentOS server's network by configuring firewall rules and provides some code examples.

However, firewalls are only one part of network security. They also need to be combined with other security measures, such as updating operating systems and applications in a timely manner, using strong passwords, restricting remote access, etc., to improve the overall security of the server. By always being vigilant and learning about the latest security technologies, we can better protect our servers and data.

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