To ensure the security of Node JS applications, several best practices can be followed. These include using secure coding practices, such as input validation and output encoding, to prevent common web application vulnerabilities. It is also important to keep dependencies up-to-date to avoid potential vulnerabilities in third-party libraries. Implementing authentication and authorization mechanisms, such as user roles and permissions, can help prevent unauthorized access to sensitive data. Regular security testing, such as vulnerability assessments and penetration testing, can help identify and address security issues before they are exploited. Finally, implementing security measures at the infrastructure level, such as firewalls and intrusion detection systems, can provide an additional layer of protection for Node JS applications.