An SQL injection is a type of attack that inserts malicious code inside a website's information system. It is a way of manipulating websites to gain access to hidden information or inject potentially malicious SQL commands into a database. There are several ways to prevent an SQL injection attack, such as input validation, parameterized queries, and adequate database security.

1. Implement input validation checks to identify and block malicious user input
2. Limit user access and privileges, and create a strong password policy
3. Encrypt user data
4. Set up isolation networks for user access
5. Use parameterized queries
6. Keep the database and software updated with the latest security patch
7. Audit the database regularly for potential integrity vulnerabilities
8. Keep plans and designs of the database architecture secure