What is SQL injection?

SQL injection is a type of security vulnerability that occurs in the database layer of an application. It is a code injection technique that might allow an attacker to interfere with the queries that an application makes to its database. It usually involves the insertion or “injection” of a SQL query via the input data from the client to the application. A successful SQL injection exploit can read sensitive data from the database, modify database data (Insert/Update/Delete), execute administration operations on the database (such as shutdown the DBMS), recover the content of a given file present on the DBMS file system and, in some cases, issue commands to the operating system. SQL injection can occur in any database or data-driven application that uses SQL, including websites, web applications, and custom applications.

To protect against SQL injection, one should:

1. Use prepared statements with parameterized queries. These are SQL queries where the parameters (inputs from the user or application) are not concatenated directly into the query string but are sent using a different mechanism, allowing the database to distinguish between code and data.
2. Use stored procedures, which can help limit SQL injection if correctly used, as they also require the use of parameterized input. However, dynamic SQL within stored procedures can still be vulnerable.
3. Validate and sanitize all user inputs to restrict the insertion of malicious SQL. This includes typing the input and length restrictions.
4. Escaping all user inputs, although not as effective as parameterized queries, can help mitigate SQL