Google dorks are search operators used to refine Google searches. They can be used to access secure webpages, download files, or access security cameras. Common dorks include "site:", "inurl:", "intitle:", and "filetype:" or "ext:". SQL injection is a code injection technique that exploits security vulnerabilities in database applications. It works by inserting SQL commands into user input fields to alter the meaning of SQL queries and gain unauthorized access to databases. Defenses include input validation, prepared statements, limiting privileges, and intrusion detection systems.