A SQL injection attack is a type of cyberattack where an attacker inserts or “injects” malicious SQL code into an application’s input fields, such as web forms, URLs, or cookies, with the goal of manipulating the application’s database queries. This vulnerability arises when user-supplied data is improperly handled or validated by the application, allowing the attacker’s input to be executed as part of a SQL command.
How SQL Injection Works
- User Input Manipulation: The attacker provides specially crafted input that alters the intended SQL query. For example, instead of entering a username, the attacker might enter a string like ‘ OR 1=1 –, which changes the logic of the query to always return true.
- Query Modification: The application concatenates this input directly into a SQL statement without proper sanitization, causing the database to execute unintended commands.
- Potential Actions: Attackers can use SQL injection to:
- Retrieve sensitive data (e.g., user information, credit card numbers)
- Modify or delete data
- Execute administrative operations on the database
- Bypass authentication mechanisms
- In some cases, execute commands on the underlying server.
Suppose an application executes the following SQL query to authenticate users:
SELECT * FROM users WHERE username = ‘[user_input]’ AND password = ‘[user_input]’
If an attacker enters admin’ — as the username and anything as the password, the query becomes:
SELECT * FROM users WHERE username = ‘admin’ –‘ AND password = ‘[anything]’
The — starts a comment in SQL, so the password check is ignored, potentially granting unauthorized access.