SQL Injection is a type of injection attack that makes it possible to execute malicious SQL statements. These statements control a database server behind a web application. Attackers can use SQL Injection vulnerabilities to bypass application security measures. They can go around authentication and authorization of a web page or web application and retrieve the content of the entire SQL database. They can also use SQL Injection to add, modify, and delete records in the database.

An SQL Injection vulnerability may affect any website or web application that uses an SQL database such as MySQL, Oracle, SQL Server, or others. SQL Injection attacks are one of the oldest, most prevalent, and most dangerous web application vulnerabilities.

Parameterized Statements

Parameterized statements make sure that the parameters (i.e. inputs) passed into SQL statements are treated in a safe manner.

Sanitizing Inputs

Client-side validation (i.e. in JavaScript) is useful for giving the user immediate feedback when filling out a form but is no defense against a serious hacker. Most hack attempts are performed using scripts, rather than the browser itself.

How and Why is an SQL Injection Attack Performed?

To make an SQL Injection attack, an attacker must first find vulnerable user inputs within the web page or web application. A web page or web application that has an SQL Injection vulnerability uses such user input directly in an SQL query. The attacker can create input content. Such content is often called a malicious payload and is the key part of the attack. After the attacker sends this content, malicious SQL commands are executed in the database.

SQL is a query language that was designed to manage data stored in relational databases. You can use it to access, modify, and delete data. Many web applications and websites store all the data in SQL databases.

  • Attackers can use SQL Injection to find the credentials of other users in the database. They can then impersonate these users. The impersonated user may be a database administrator with all database privileges.
  • SQL also lets you alter data in a database and add new data. For example, in a financial application, an attacker could use SQL Injection to alter balances, void transactions, or transfer money to their account.
  • SQL can be used to delete records from a database, even drop tables. Even if the administrator makes database backups, the deletion of data could affect application availability until the database is restored. Also, backups may not cover the most recent data.
  • In some database servers, you can access the operating system using the database server. This may be intentional or accidental. In such a case, an attacker could use an SQL Injection as the initial vector and then attack the internal network behind a firewall.