How to protect against auto-submit attacks using PHP forms

With the continuous development of network technology and the widespread use of network applications, security issues have increasingly attracted people's attention. Among them, automatic submission attacks are a common network attack method and one of the security threats faced by many websites. This article will introduce how to use PHP forms to prevent automatic submission attacks.

1. What is an automatic submission attack?

An automatic submission attack means that the attacker automatically submits form data through a program to simulate human operations, thereby achieving the purpose of illegally obtaining information or destroying the website. Automatic submission is generally divided into two methods: automated tool submission and script submission. Automated tool submission is to use ready-made tool programs to perform submission operations; script submission is to write script programs to simulate submission operations, which can better disguise as a normal user.

2. How to use PHP forms to prevent automatic submission attacks

1. Use verification code

Verification code is a common way to prevent automatic submission attacks. This can be achieved by adding a verification code field to the form. The verification code is generally an image containing randomly generated characters or numbers that the user needs to enter correctly to submit the form. In PHP, you can easily generate verification code images using the GD library.

2. Use hidden fields

Using hidden fields is also an effective way to prevent automatic submission attacks. Add a hidden field to the form. Since the attacker cannot see the field, it cannot be filled in correctly, thereby preventing attacks. To use this method, ensure that the names and parameters of hidden fields are not exposed in client code.

3. Set and verify the source page

When the form is submitted, the source page information can be obtained through the $_SERVER['HTTP_REFERER'] variable. The submitted form can be verified to ensure that the form comes from this site and that this site has not been linked to by other websites. Verifying the source page can effectively prevent automatic submission attacks, but there are also some problems. For example, some browsers may disable HTTP Referer, resulting in verification failure.

4. Delayed submission

Delayed submission refers to adding a time judgment before the form is submitted. If the submission time is too short, it is judged to be automatically submitted. The implementation method is to add a hidden field to the form to record the current time. Then when the form is submitted, it is compared with the time recorded in the hidden field. If the time interval is too short, it is judged to be automatically submitted and the submission request is rejected.

5. Increase input restrictions

In PHP, you can use regular expressions and other methods to limit input content to ensure the validity and security of form data. For example, you can restrict the format of input content such as email addresses, phone numbers, and ID numbers.

3. Summary

How to prevent automatic submission attacks is an important issue in website security. Automatic submission attacks can be effectively prevented by using methods such as verification codes, hidden fields, verification of source pages, delayed submission, and input restrictions. However, attack methods are constantly changing, and PHP programmers need to constantly update their security knowledge to keep pace with the times.

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