The risk described is increased attack surface caused by unnecessary services and protocols running on a web server—specifically NetBIOS and SMB. The most direct hardening action to mitigate this is to block/disable unnecessary ports and protocols so they are not exposed to the network and cannot be abused by attackers. Option D captures that principle: reduce exposure by closing ports and restricting protocols that are not required for the server’s role.
A well-hardened web server should run only the services needed to deliver its intended web functionality (e.g., HTTP/HTTPS and necessary management interfaces under strict control). Services like SMB (commonly TCP 445/139) and NetBIOS (UDP 137/138, TCP 139) are not normally required for public-facing web hosting and are frequent targets for enumeration and exploitation. Leaving such services open can enable attackers to perform credential attacks, exploit legacy vulnerabilities, access shared resources, or pivot further into the environment. By blocking or disabling these ports at the host firewall and/or perimeter firewall, the organization reduces reachable attack paths and limits what an external attacker can interact with.
Why the other options are less direct:
Dedicated machine (A) can help separation of duties, but if unnecessary services still run, the attack surface remains.
Risk assessment for patching (B) is important, but it doesn’t immediately remove the exposure created by unneeded services.
Eliminating unnecessary files (C) addresses file-system exposure, not open network services like SMB/NetBIOS.
Because the problem is explicitly about unnecessary open services/protocols, the best mitigation is D. Block all unnecessary ports, ICMP traffic, and protocols (i.e., minimize exposed services).
