Which security technology is specifically designed to monitor and block unauthorized access to a network?

The security technology that is specifically designed to monitor and block unauthorized access to a network is the firewall. A firewall acts as a barrier between a trusted internal network and untrusted external networks, such as the internet. It controls incoming and outgoing traffic based on predetermined security rules, thus preventing unauthorized access while allowing legitimate traffic to pass through.

Firewalls can be hardware-based, software-based, or a combination of both. They inspect data packets and determine whether they should be allowed through or blocked, effectively protecting the network from external threats such as intrusions or attacks.

In contrast, other choices do not serve the same primary function. For example, an Intrusion Detection System (IDS) monitors network traffic for suspicious activities or policy violations but does not actively block traffic. Instead, it alerts administrators to potential security breaches. A Virtual Private Network (VPN) is designed to create secure connections over the internet, providing privacy and protection for data in transit, but it does not specifically monitor or block unauthorized access to the network itself. Network Behavior Analysis is a technology focused on monitoring and analyzing network traffic patterns to detect anomalies that could indicate a threat or potential breach, but like the IDS, it does not block access.

Therefore, the firewall is the most suitable answer