Which of the following threats is least effectively controlled by a…

A traditional hardware firewall sits at the network perimeter and filters traffic flowing between the internal network and the outside world, allowing or blocking packets based on rules such as IP addresses, ports and protocols.

Because of this perimeter role, a firewall is effective against externally originated threats: it can block unauthorized port access, drop malicious inbound traffic, stop external intrusion attempts and deny unauthorized external network access. All four of these are perimeter-facing threats the firewall is designed to handle.

However, a firewall offers little protection against an insider threat. When an authorized internal user steals data, the activity originates from inside the trusted network using legitimate credentials, so it usually does not cross the perimeter firewall in a way the firewall can inspect or block. The firewall cannot distinguish legitimate use from misuse by someone who already has authorized access.

Therefore, the threat least effectively controlled by a traditional hardware firewall is data theft by authorized internal users. Mitigating insider threats requires complementary controls such as access management, Data Loss Prevention (DLP), user-activity monitoring and behaviour analytics, not a perimeter firewall.

Hence, the correct answer is "Data theft by authorized internal users."