SQL Injection

SQL injection is a type of security vulnerability that allows an attacker to inject malicious SQL code into a SQL statement, which can then be executed by the database. This can allow the attacker to bypass security measures and access or modify data in the database.

SQL injection attacks typically occur when input from an external source (such as a user's input in a web application) is not properly sanitized or validated before being used in a SQL statement. For example, consider the following SQL statement:

SELECT * FROM users WHERE username = 'username' AND password = 'password';

If the values for username and password are supplied by the user, an attacker could potentially insert malicious SQL code as the input, such as:

username = 'admin' --
password = 'password'

This would result in the following SQL statement being executed:

SELECT * FROM users WHERE username = 'admin' --' AND password = 'password';

The double dash (--) is a comment marker in SQL, which causes everything after it to be ignored. This means that the attacker can bypass the password check entirely and access any account with the username admin.

To prevent SQL injection attacks, it is important to always sanitize and validate input from external sources before using it in a SQL statement. This can be done by using parameterized queries, which allow input values to be passed as parameters rather than being directly embedded in the SQL statement. For example:

SELECT * FROM users WHERE username = ? AND password = ?;

In this case, the actual values for username and password are supplied as parameters to the query, rather than being directly embedded in the SQL statement. This makes it much harder for an attacker to inject malicious code into the statement.