As Internet security becomes increasingly important, DDoS (distributed denial of service) attacks have become a common network threat, which has had a serious impact on many online services and enterprises. In order to deal with such attacks, reverse proxy technology has been adopted by more and more enterprises and organizations. So, what exactly is a reverse proxy? How does it help defend against DDoS attacks? This article will explore this issue in detail and provide a comprehensive solution.

What is a reverse proxy?

A reverse proxy is a server that sits between the client and the actual server and acts as an intermediary. Unlike traditional forward proxies, reverse proxies do not directly process requests from users, but respond to client requests on behalf of the server. Simply put, a reverse proxy proxies requests from the server instead of the client.

Common reverse proxy servers include Nginx, Apache HTTP Server, and HAProxy. They can receive requests from clients and forward them to one or more internal backend servers according to preset rules. This method prevents external users from directly accessing the backend servers, thereby improving security.

Reverse proxies can not only be used for load balancing, SSL termination, caching, acceleration and other functions, but can also effectively deal with various network attacks, especially DDoS attacks.

How does a reverse proxy work?

The working method of a reverse proxy is relatively simple. Its main function is to receive requests from external clients and forward the requests to the actual server for processing according to certain rules. The processed response data will be returned to the client, thus completing the communication between the client and the actual server.

Specifically, the working process of a reverse proxy includes the following steps:

The client sends a request

The client sends a request, usually to access a specific web page or application.

Reverse proxy receives a request

After receiving the client's request, the reverse proxy server will first perform a series of security checks (such as filtering malicious requests, checking firewalls, etc.).

Forwarding requests to backend servers

If the request is legitimate and secure, the reverse proxy server will forward the request to one or more backend servers for processing according to the load balancing strategy.

The backend server processes the request and responds

After the backend server processes the request, it returns the response result to the reverse proxy server.

The reverse proxy returns the client response

After receiving the response from the backend server, the reverse proxy sends the response content back to the client.

Through this process, the reverse proxy can centrally manage all client requests, thereby effectively shielding the specific information of the internal server, preventing direct external access to the server, and improving security.

How does the reverse proxy prevent DDoS attacks?

DDoS attacks use a large number of false requests to prevent the target server from processing legitimate requests normally, causing the website or application to be paralyzed. As an effective middle-layer technology, the reverse proxy plays an important role in defending against DDoS attacks. The following are several ways how the reverse proxy responds to DDoS attacks:

1. Hide the real server IP

One of the most basic functions of the reverse proxy is to hide the real backend server IP address. When a user accesses a website through a reverse proxy, the client actually accesses the reverse proxy's IP address instead of the actual server's IP address. The attacker cannot directly obtain the server's address, thereby reducing the risk of targeted attacks.

2. Traffic filtering and cleaning

Reverse proxies can filter malicious traffic by combining with tools such as WAF (Web Application Firewall). By detecting the source, content, and behavior patterns of requests, reverse proxies can identify and block abnormal traffic, such as requests from botnets. This traffic filtering can effectively reduce the pressure of DDoS attacks.

3. Load balancing and traffic distribution

Reverse proxies can distribute incoming traffic to multiple servers through load balancing technology to prevent a single server from becoming a bottleneck for DDoS attacks. When traffic surges, reverse proxies can automatically expand the system to share the load and ensure that the server can handle all normal requests.

4. Rate limiting and access control

Reverse proxies can also implement rate limiting to limit the frequency of requests initiated by each IP address within a certain period of time. By setting access restrictions, reverse proxies can effectively prevent attackers from exhausting server resources through a large number of requests and prevent DDoS attacks from being successful.

5. Cache static content

Reverse proxies can cache static content (such as images, CSS files, and JavaScript scripts) and respond directly to user requests. This can reduce the burden on the backend server and protect it from DDoS attacks by reducing the frequency of access to the backend server.

Benefits of reverse proxy

In addition to preventing DDoS attacks, reverse proxy has many other benefits that make it an indispensable part of modern Internet architecture:

1. Improve security

Reverse proxy isolates external requests from internal servers, reducing the risk of directly exposing backend services. It can effectively prevent security issues such as hacker attacks and data leaks.

2. Load balancing and high availability

Reverse proxy can achieve load balancing, evenly distribute traffic to multiple servers, and ensure that the system can remain stable when traffic surges. This is essential for websites and applications that handle high traffic.

3. Simplify network architecture

With reverse proxy, all external requests enter through the same entry point, thereby simplifying the network architecture. For large websites, reverse proxy can manage traffic uniformly and reduce the burden on the server.

Disadvantages of reverse proxy

1. Setting up and maintaining a reverse proxy may be more complicated than managing a single web server.

2. If a reverse proxy fails, it may affect access to all web servers behind it.

3. Deploying a reverse proxy requires additional server resources and infrastructure, which may increase costs.