This document discusses database security, threats, and countermeasures. It defines database security as protecting the confidentiality, integrity, and availability of database data. Common threats include unauthorized access, data corruption, and network issues. Countermeasures include access control, authorization, encryption, backups, and firewalls. Firewalls monitor network traffic to identify and block harmful queries. Encryption uses keys to securely store and decrypt data. Authorization controls user permissions. These controls help secure database data from both intentional and accidental threats.