Deep Dive: SQL Injection Explained

SQL injection exploits poorly coded websites that don't validate user input. Here's a step-by-step example:

Normal login process:

• User enters username: alice
• Website creates SQL query: SELECT * FROM users WHERE username='alice'
• Database checks if 'alice' exists and returns the user record

SQL injection attack:

• Attacker enters username: ' OR '1'='1
• Website creates SQL query: SELECT * FROM users WHERE username='' OR '1'='1'
• Since '1'='1' is ALWAYS true, this returns ALL users - bypassing authentication!
• Attacker gains unauthorized access without knowing any passwords

Prevention methods:

• Input validation: Check that inputs match expected format (e.g., usernames contain only letters/numbers)
• Input sanitization: Remove or escape special characters like quotes
• Parameterised queries: Separate SQL code from user data so injected code isn't executed
• Prepared statements: Pre-compile SQL queries so user input can't alter query structure