Which type of firewall is known for blocking network access from external networks while potentially causing latency issues?

A proxy firewall operates at the application layer and serves as an intermediary between users and the services they wish to access. It inspects and filters traffic before it reaches the destination, which enhances security by blocking unwanted external network access. This method of handling traffic can introduce latency since the firewall processes and evaluates data packets closely, causing delays in communication.

The proxy firewall's architecture, which may involve buffering and analyzing the entire content, adds to the time taken for requests and responses compared to other types of firewalls that might not inspect every packet in such detail. This thorough inspection is valuable for security but can compromise speed, especially in high-traffic environments where frequent connections are made.

In contrast, stateful inspection firewalls maintain a table of active connections and only inspect packets within those connections, typically leading to better performance. Web application firewalls focus on securing web applications from specific attacks, and deep inspection firewalls analyze deeper across multiple layers of data. While all these types are effective in their respective contexts, the proxy firewall's fundamental operation is what is known to contribute to potential latency issues.