SQL Injection is a type of security vulnerability that occurs when an attacker injects malicious SQL code into a web application's database. This can result in unauthorized access to sensitive data, modification of data, or even complete destruction of the database.
SQL Injection attacks are one of the most common types of attacks on web applications. They are often used by attackers to gain access to sensitive information such as usernames, passwords, and credit card numbers. SQL Injection attacks can be devastating to businesses and individuals alike, as they can result in financial loss, identity theft, and other serious consequences.
There are several ways in which SQL Injection attacks can be carried out. One common method is through the use of input fields on a web form. An attacker can enter malicious SQL code into these fields, which is then executed by the web application's database. Another method is through the use of URL parameters, where an attacker can add SQL code to the end of a URL in order to execute it.
Here is an example of a SQL Injection attack:
SELECT * FROM users WHERE username = 'admin' AND password = 'password'
An attacker could inject malicious SQL code into this query, such as:
SELECT * FROM users WHERE username = 'admin' OR 1=1 --' AND password = 'password'
This code would return all users in the database, as the "OR 1=1" statement is always true. The "--" at the end of the code is used to comment out the rest of the query, so that the password check is ignored.
There are several ways to prevent SQL Injection attacks. One method is to use parameterized queries, which separate the SQL code from the user input. Another method is to sanitize user input, which involves removing any potentially malicious characters from the input before it is used in a query.
Here is an example of a parameterized query:
$stmt = $pdo->prepare('SELECT * FROM users WHERE username = :username AND password = :password');
$stmt->execute(array('username' => $username, 'password' => $password));
Here is an example of sanitizing user input:
$username = mysqli_real_escape_string($conn, $_POST['username']); $password = mysqli_real_escape_string($conn, $_POST['password']);
By using these methods, web developers can help prevent SQL Injection attacks and protect their users' sensitive information.