Which of the following is a method to secure client and employee data?

Masking credit card and social security numbers is an effective method for securing client and employee data because it involves altering sensitive information to prevent unauthorized access while still allowing data to be processed and utilized for necessary operations. By replacing sensitive data with pseudonyms or symbols, organizations can protect personal information against potential breaches while maintaining the integrity of their systems. This approach ensures that even if data is accessed by individuals who should not have it, they will be unable to view the actual sensitive information, thus reducing the risk of identity theft and fraud.

The other methods mentioned do not contribute positively to data security. Storing data on a public server exposes it to a wider audience, increasing the risk of unauthorized access. Using unprotected files for easy access compromises data security, making it easier for malicious actors to exploit vulnerabilities. Leaving computers logged in unattended can also lead to unauthorized access, as anyone could use the unlocked system to view or manipulate sensitive data.