What is SQL Injection

SQL injection is a type of security exploit that can compromise the security of a database-driven application. It occurs when an attacker injects malicious SQL code into a web form input box, which is then executed by the application's database server. This can result in sensitive information being stolen, manipulated or destroyed, or unauthorized access being gained to an application's back-end database.

The basic principle behind SQL injection is that an attacker is able to execute unauthorized SQL queries by manipulating the data that is submitted to an application's database server. This can be achieved by exploiting vulnerabilities in an application's code that allow user input to be interpreted as SQL commands.

SQL injection attacks can have devastating consequences for both users and businesses. Users can have their personal information compromised, such as usernames, passwords, credit card numbers, and other sensitive data. Businesses can suffer from reputational damage, financial losses, and legal liability if they fail to adequately protect their customers' data.

How SQL Injection Works

SQL injection is a technique used by hackers to attack a website's database by inserting malicious SQL statements into an entry field, such as a login form or search box. The goal is to trick the website into executing the malicious SQL code and providing access to sensitive data, such as usernames and passwords.

The attack works by exploiting vulnerabilities in the website's code that allow user input to be executed as SQL commands. For example, an attacker might enter a specially crafted string into a search box that contains SQL commands. If the website's code fails to properly sanitize or validate the input, the SQL commands will be executed, giving the attacker access to the database.

Once the attacker gains access to the database, they can steal, modify, or delete data at will. They can also use the database to launch further attacks on the website or its users.

Types of SQL Injection Attacks

There are several types of SQL injection attacks that attackers can use to exploit vulnerabilities in an application's code:

Classic SQL Injection

This is the most common type of SQL injection attack. In this attack, the attacker uses a web form or URL parameter to inject SQL code into the application's database query. The attacker can then execute their own SQL commands on the database, giving them access to sensitive information.

Blind SQL Injection

In a blind SQL injection attack, the attacker sends SQL commands to the application's database, but does not receive any output from the database. This can make the attack more difficult to detect, as the attacker cannot see the results of their actions.

Error-Based SQL Injection

In an error-based SQL injection attack, the attacker injects SQL code that causes the database to generate an error. The error message can then reveal information about the structure of the database or the data stored within it.

Union-Based SQL Injection

In a union-based SQL injection attack, the attacker injects SQL code that combines the results of two or more database queries. This can allow the attacker to retrieve information from multiple tables within the database.

Time-Based SQL Injection

In a time-based SQL injection attack, the attacker injects SQL code that causes the database to delay its response. This can allow the attacker to infer information about the database structure or data stored within it based on the time it takes to receive a response.

Second-Order SQL Injection

In a second-order SQL injection attack, the attacker injects SQL code into the application's database, but the code is not executed until a later time, such as when an administrator logs into the system.

Examples of SQL Injection Attacks

SQL injection attacks are a serious threat to web applications that use databases. These attacks can compromise the confidentiality, integrity, and availability of sensitive information. There have been numerous real-world examples of SQL injection attacks in recent years, some of which have had significant consequences. Here are a few notable examples:

• Equifax
  In 2017, Equifax, one of the largest credit reporting agencies in the United States, suffered a massive data breach that exposed the personal information of over 143 million customers. The breach was caused by a vulnerability in the company's web application that allowed hackers to execute a SQL injection attack and gain access to the sensitive data.

• US Democratic National Committee
  In 2016, hackers used a SQL injection attack to breach the Democratic National Committee's database and steal sensitive information. The attack was carried out by injecting malicious code into the committee's web application.

• Yahoo
  In 2012, hackers used a SQL injection attack to breach Yahoo's database and steal the login credentials of more than 450,000 users. The attackers were able to gain access to the database by injecting malicious code into a Yahoo subdomain.

• TalkTalk
  In 2015, TalkTalk, a UK-based telecommunications company, suffered a data breach that exposed the personal information of over 150,000 customers. The breach was caused by a SQL injection attack that exploited a vulnerability in the company's website.

• Ubuntu Forums
  In 2013, hackers used a SQL injection attack to breach Ubuntu Forums, a popular online community for Ubuntu Linux users. The attack resulted in the theft of usernames, email addresses, and passwords.

Preventing SQL Injection Attacks

SQL injection attacks are a type of cyber attack that can have serious consequences, including data theft, data manipulation, and system compromise. However, there are several best practices that can help prevent these types of attacks. Here are some effective ways to prevent SQL injection attacks:

• Input Validation
  One of the most important steps to prevent SQL injection attacks is to validate all user input. This includes validating form data, URL parameters, and any other data that is sent to the server. This can be done by using regular expressions or other validation techniques to ensure that the data is in the expected format and does not contain any malicious code.

• Sanitization
  Sanitization involves removing any potentially harmful characters or code from user input before it is used in a SQL query. This can be done by using functions that remove or escape special characters such as quotes, semicolons, and backslashes.

• Prepared Statements
  Prepared statements are a way to parameterize SQL queries so that user input is never directly included in the query. This means that even if an attacker is able to inject malicious code into the input, the code will not be executed as part of the SQL query.

• Least Privilege
  It is important to limit the privileges of database users to only what is necessary for them to perform their job. For example, a user who only needs to read data should not have write access to the database.

• Regular Security Audits
  Regular security audits can help identify vulnerabilities in web applications that could be exploited by SQL injection attacks. This can include code reviews, vulnerability scanning, and penetration testing.

By following these best practices, developers can significantly reduce the risk of SQL injection attacks in their web applications. It is important to stay vigilant and keep up with the latest security trends to ensure that your web application is secure from these types of attacks.

References

https://www.w3schools.com/sql/sql_injection.asp
https://portswigger.net/web-security/sql-injection
https://cheatsheetseries.owasp.org/cheatsheets/SQL_Injection_Prevention_Cheat_Sheet.html
https://www.acunetix.com/websitesecurity/sql-injection/