Which method is commonly used to improve network security?

Using a Virtual Private Network (VPN) is a widely recognized method for enhancing network security. A VPN creates a secure and encrypted connection over a less secure network, such as the Internet. This secure tunnel helps protect sensitive data from interception by encrypting the transmitted information, ensuring that it remains private and integral against potential eavesdroppers or attackers.

Additionally, VPNs allow users to securely access the organization's internal network remotely, which is particularly beneficial for organizations with telecommuting employees or those that require secure connections while traveling. By employing a VPN, organizations can maintain data confidentiality and integrity while facilitating legitimate access to resources.

The other options do not provide enhanced security in the same manner. Implementing a guest Internet access policy is about managing access but does not secure data transmission. Eliminating all software firewalls undermines security by removing protective measures against unauthorized access and malicious traffic. Similarly, disabling all remote access can limit operational efficiency and doesn't address potential security risks associated with authorized access attempts.