How to use Nginx to protect against port scanning attacks

In the current Internet environment, security has always been one of the most concerning issues for network administrators and website developers. Among them, port scanning attacks are a common security vulnerability. Attackers scan open ports on a website to identify potential vulnerabilities. In order to avoid security threats caused by port scanning attacks, more and more enterprises and websites choose to use Nginx as their web server. This article will introduce how to use Nginx to prevent port scanning attacks.

1. What is a port scanning attack?

Port scanning means that the attacker uses TCP or UDP protocols to scan all ports of the target server to find potential vulnerabilities or services. The information obtained by the attacker through port scanning can be used for further attacks, such as flood attacks (DDoS) or intrusion into servers. Since port scanning is usually automated by programs, attackers can easily scan all IP addresses across the Internet to find security holes that pose significant threats.

2. How does Nginx prevent port scanning?

1. Configuration to restrict access

In the Nginx configuration file, you can set up to allow or prohibit specific IP addresses or IP address ranges from accessing the server. In this way, when opening a port, only specific IP addresses or IP address ranges are allowed to access, which can effectively limit attackers from scanning the server.

For example, the following configuration only allows clients with IP addresses 192.168.0.1 and 192.168.0.2 and the IP address segment 192.168.1.0/24 to access the Nginx server:

location / {
    allow 192.168.0.1;
    allow 192.168.0.2;
    allow 192.168.1.0/24;
    deny all;
}

2. Configuration Firewall

Nginx’s reverse proxy and load balancing functions can be used in conjunction with firewalls to improve server security. Through the firewall's filtering rules, it is possible to limit traffic and define rules such as blocking IP addresses for port scanning. At the same time, Nginx reverse proxy can also redirect traffic from the client to the backend web server, thereby hiding the real web server IP address and increasing security.

3. Turn on the SO_REUSEPORT option

SO_REUSEPORT is an option provided by the Linux kernel, which allows sockets to share the same port to reduce the risk of port exhaustion and improve load balancing. ability. By turning on the SO_REUSEPORT option, multiple Nginx processes can be allowed to listen to the same port at the same time, strengthening the load balancing function and improving server security.

For example, add the following content to the configuration file to enable the SO_REUSEPORT option:

worker_processes auto;
worker_cpu_affinity auto;
worker_rlimit_nofile 10000;
reuseport on;

3. Summary

In order to avoid the security threat caused by port scanning attacks to the server, Nginx It has become the preferred web server for more and more enterprises and websites. Through the above methods, the security of the server can be effectively strengthened and attackers can be restricted from scanning the server, thus improving the security of data and information. At the same time, it is also necessary to strengthen system security management and network monitoring to detect and deal with security issues in a timely manner.

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