How to prevent denial of service attacks using PHP

A Denial of Service attack (DDoS) is a bad actor sending a large number of network requests to a server so that it cannot respond normally to requests from real users. This attack method is very dangerous for the server because it can make the server unusable, making it impossible for real users to access it normally. In order to prevent denial of service attacks, we can take a series of measures in PHP programs.

Step One: Limit the Request Frequency
The attacker will conduct a denial of service attack by sending a large number of network requests to the server. So we can prevent this attack by limiting the request frequency. The specific method can be to add a check in the back-end server. If a user sends too many requests to the server in one second, directly reject the request, or add a verification code and other human-machine verification functions, so as to effectively to slow down the attack.

Step 2: Add Web Application Firewall (WAF)
Web application firewall can prevent denial of service attacks in many aspects, including SQL injection, cross-site scripting attacks, file inclusion vulnerabilities, etc. These vulnerabilities are Can be used by attackers to launch denial of service attacks. At the same time, WAF can also perform functions such as current limiting and anti-crawling, thereby effectively preventing attacks. WAF can usually be used as a plug-in for Nginx, Apache or other web servers, or it can use the services of a cloud security platform.

Step 3: Use CDN acceleration and manual authentication mechanism
Mainly used to quickly load static resources, such as javascript, images and CSS; the manual authentication mechanism can filter out illegal and malicious ones to a certain extent ask. At the same time, CDN can also provide anti-DOS function, that is, it can detect that a certain IP has generated too many HTTP requests in a short period of time, and blacklist its IP address, thereby filtering out some unnecessary access.

Step 4: Use IP Black and White List
If you have access control requirements or need to only allow specific IP addresses or a set of alternate IP addresses to access your application, you can use IP Black and White Lists to prevent DOS attack. This approach is typically targeted at development or test environments and may be less effective for production environments.

In short, preventing denial of service attacks requires a combination of methods, such as limiting request frequency, adding a web application firewall, using CDN acceleration and manual authentication mechanisms, using IP black and white lists, etc. But the combination of different measures can achieve twice the result with half the effort. During the PHP programming process, developers should strengthen attack prevention for different application scenarios.

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