SQL Injection Attacks: How to be Aware?
Estimated study time: 8 minutes. Understand the risk and the defenses every developer should know.
SQL Injection is one of the oldest and most damaging security vulnerabilities in database-driven applications. It happens when untrusted user input is inserted directly into a SQL query, letting an attacker manipulate that query.
How It Happens
Imagine a login query built by concatenating user input directly into a string:
string query = "SELECT * FROM Users WHERE Username = '" + username + "' AND Password = '" + password + "'";
If an attacker enters ' OR '1'='1 as the username, the query effectively becomes always true, bypassing authentication entirely.
Common Types of SQL Injection
- Classic/In-band Injection — results are returned directly in the application's response.
- Blind Injection — no data is shown directly; the attacker infers information from true/false behavior or response timing.
- Out-of-band Injection — data is exfiltrated through a different channel, like DNS or HTTP requests.
How to Protect Against It
1. Use Parameterized Queries
SELECT * FROM Users WHERE Username = @Username AND Password = @Password;
Parameters are sent separately from the query text, so user input can never change the query's structure.
2. Use Stored Procedures Correctly
Stored procedures help, but only if you still pass values as parameters rather than building dynamic SQL by string concatenation inside them.
3. Apply the Principle of Least Privilege
Give application accounts only the permissions they truly need — no unnecessary DROP, ALTER, or cross-database access.
4. Validate and Sanitize Input
Enforce expected data types, lengths, and formats at the application layer as an additional defense, not a replacement for parameterized queries.
5. Use an ORM Where Practical
Tools like Entity Framework or Dapper parameterize queries by default, reducing the chance of accidental raw string concatenation.