What security technique could provide secure access to a server located in a small office without the expense of implementing a DMZ or purchasing a hardware firewall?

Using a VPN (Virtual Private Network) is an effective security technique for providing secure access to a server located in a small office, especially when considering cost-effective solutions over implementing a DMZ or purchasing a hardware firewall. A VPN creates a secure and encrypted tunnel for data traffic between the user's device and the server, ensuring that sensitive information is safeguarded from unauthorized access.

When a user connects to the network via a VPN, it helps maintain privacy and data integrity while communicating with the server. It also allows remote users to access the local network securely as if they were physically present in the small office. This method is often seen as more cost-effective because it typically requires only software solutions and does not involve the complexities and expenses associated with additional hardware like firewalls or DMZ setups.

In this scenario, while port forwarding allows specific traffic to be routed to a particular server, it does not provide the same level of security as a VPN, which encrypts traffic and protects against eavesdropping. Other options like network segmentation and proxy servers come with their own sets of requirements and costs that may not align with the goal of providing a straightforward, secure access method for a small office environment.