20 PHP Security Interview Questions and Answers

As a PHP developer, you should be well-versed in the language’s security features. This includes being able to identify and mitigate common security risks. When interviewing for a position, you may be asked questions about PHP security risks and how to mitigate them. Answering these questions confidently can help you secure the job. In this article, we review some of the most common PHP security questions and how to answer them.

PHP Security Interview Questions and Answers

Here are 20 commonly asked PHP Security interview questions and answers to prepare you for your interview:

1. What is a SQL injection attack?

A SQL injection attack is a type of attack where a malicious user tries to insert SQL code into a web form in order to access or change data in the database. This can be done by adding SQL code into input fields on a web page or by sending SQL code as part of a URL. If the web application does not properly sanitize the user input, then the SQL code can be executed and the attacker can gain access to sensitive data or make changes to the database.

2. Is it possible to prevent SQL injection attacks in PHP code? If yes, then how can you do so?

Yes, it is possible to prevent SQL injection attacks in PHP code. One way to do this is to use parameterized queries, which will ensure that only the data that is supposed to be inserted into the database is actually inserted. Another way to prevent SQL injection attacks is to use prepared statements, which will also help to ensure that only the correct data is inserted into the database.

3. Can you explain what the MVC pattern is and why is it important for security?

MVC is an important software design pattern that helps to keep code organized and modular. This is important for security because it helps to prevent code from becoming tangled and difficult to understand. It also makes it easier to spot potential security vulnerabilities. By keeping code organized, MVC can help to make your applications more secure.

4. How can you implement user authentication with strong password hashing in PHP?

There are a few different ways to implement user authentication with strong password hashing in PHP. One way would be to use the password_hash() function to hash the user’s password before storing it in the database. Then, when the user tries to log in, you can use the password_verify() function to check that the hash of the password they provided matches the hash in the database. Another way would be to use a library like PHPass, which provides a variety of hashing algorithms to choose from.

5. What are some examples of common cross-site scripting (XSS) vulnerabilities?

One example of a cross-site scripting vulnerability is when a user input field does not properly sanitize user input before displaying it back to the user. This can allow an attacker to inject malicious code into the field that will be executed by the user’s browser when they view the page. Another example is when a website includes user-supplied data in its HTML without properly encoding it first. This can allow an attacker to inject malicious code that will be executed by the browser when the page is loaded.

6. Why is SSL/TLS important when using cookies?

SSL/TLS is important when using cookies because it helps to ensure that the cookies are not being tampered with in transit. By encrypting the cookies with SSL/TLS, it makes it much more difficult for an attacker to intercept and modify the cookies. This helps to protect the information that is being stored in the cookies, and helps to keep the user’s session secure.

7. Why should you avoid storing sensitive data in local browser storage like Cookies?

There are a few reasons for why you might want to avoid storing sensitive data in local browser storage. First, because cookies are often stored in plain text, they can be easily accessed and read by anyone who has access to the user’s computer. Additionally, cookies can be stolen by third-party websites if the user visits them while logged into the original site – meaning that the sensitive data could be exposed to someone who wasn’t supposed to have access to it. Finally, cookies can expire, meaning that if a user doesn’t visit a site for a long period of time, the data in the cookie could be lost.

8. How can you protect against cross-site request forgery attacks?

Cross-site request forgery (CSRF) attacks are a type of attack that tricks a user into unknowingly submitting a malicious request to a website. This can be done by embedding a malicious link or form on a website that the user visits. When the user clicks on the link or submits the form, they unknowingly send a request to the website that can result in unwanted actions being taken, such as changing their password or making a purchase.

To protect against CSRF attacks, you can use a number of different techniques. One is to use a token system, where a unique token is generated for each user and included in all forms and links that are displayed to the user. When a form or link is submitted, the token is checked to make sure that it is valid and that the request is coming from the correct user. Another technique is to use HTTPS for all website communications, which will help to ensure that requests cannot be intercepted and modified by a third party.

9. In what ways does session fixation occur?

Session fixation is a type of attack where the attacker tricks a user into authenticating with a session ID that the attacker has already set. This can be done by sending the user a link to a page that the attacker controls, and then redirecting the user to the target page with the same session ID. The attacker can then use the session ID to impersonate the user and gain access to sensitive information.

10. What’s the difference between authorization and authentication?

Authentication is the process of verifying that a user is who they say they are, while authorization is the process of verifying that a user has the permissions necessary to access a particular resource. In other words, authentication is about verifying identity, while authorization is about verifying permissions.

11. What are some best practices for writing secure code in PHP?

Some best practices for writing secure code in PHP include: using the latest version of PHP, using secure development frameworks, using secure coding practices, avoiding eval() and exec(), and using secure database connections.

12. What is XSS vulnerability?

XSS is a type of security vulnerability that allows an attacker to inject malicious code into a web page. This code will then be executed by the browser of any unsuspecting user who visits the page. XSS can be used to steal information from users, redirect them to malicious websites, or even execute malicious code on their computers.

13. What is CSRF vulnerability?

CSRF is a type of attack that occurs when a malicious user tricks a victim into submitting a request to a web application that they are logged into. This can be done by embedding a malicious link or form on a website that the victim visits. When the victim clicks on the link or submits the form, they unknowingly send a request to the web application that includes their session information. This allows the attacker to perform actions on behalf of the victim.

14. What is SSI vulnerability?

SSI, or Server Side Include, is a type of vulnerability that can occur when a web server is configured to allow users to include files from a remote location. This can be exploited by an attacker in order to inject malicious code into the web page, which can then be executed by unsuspecting users who visit the page.

15. How would you use sessions to store sensitive information?

When storing sensitive information in a session, it is important to encrypt the data before storing it. This can be done using a number of different methods, but the most common is to use the mcrypt extension. Once the data is encrypted, it can be stored in the session and will be safe from prying eyes.

16. What are some other types of web application vulnerabilities besides XSS and CSRF that could affect your application?

There are many other types of web application vulnerabilities that could affect your application. Some of the most common include SQL injection, session hijacking, and cross-site scripting (XSS).

17. How can you detect whether or not your application has been compromised by an attacker?

There are a few different ways that you can detect whether or not your application has been compromised by an attacker. One way is to check the application’s logs for any unusual activity. Another way is to monitor the application for any unexpected changes in behavior. Finally, you can also run security scans of the application to look for any potential vulnerabilities.

18. What are some good strategies for detecting and responding to DoS attacks?

There are a few different strategies that can be employed in order to detect and respond to DoS attacks. One is to monitor network traffic for patterns that could indicate an attack, such as a sudden influx of traffic from a single IP address. Another is to keep track of resources that are being accessed on the server, and look for any unusual spikes in usage that could indicate an attack. Finally, it is also important to have a plan in place for how to respond to an attack once it has been detected, in order to minimize the damage that can be done.

19. What is the most common way attackers try to gain access to a system?

The most common way attackers try to gain access to a system is through brute force attacks. This is where they try to guess the password or other login credentials by trying as many different combinations as possible.

20. How do you ensure that all passwords stored on your server are encrypted?

The best way to ensure that all passwords stored on your server are encrypted is to use a hashing algorithm. A hashing algorithm is a one-way function that takes a password as input and outputs a hash. This hash is then stored in the database instead of the password itself. When a user tries to log in, the password they enter is run through the hashing algorithm and the resulting hash is compared to the one stored in the database. If they match, then the user is authenticated.