What does the layered defense approach known as defense in depth primarily increase?

The layered defense approach known as defense in depth primarily increases the effort required for an attack. This strategy involves implementing multiple security measures at different levels within an organization to protect information and information systems. By having several layers of security controls, such as firewalls, intrusion detection systems, antivirus software, and user training, attackers face more obstacles and challenges when attempting to compromise a system.

When an initial layer is bypassed or defeated, additional layers act as further barriers. This multipronged defense approach not only makes it more difficult to penetrate the system but also increases the time, resources, and skills an attacker must invest to succeed. The result is a significantly elevated effort threshold, which can deter potential attackers or even discourage them from attempting an attack altogether. This means that organizations can better protect their assets and information by making it less appealing or feasible for adversaries to launch successful incursions.

In contrast, the other options do not effectively relate to the core objective of defense in depth. The approach does not inherently aim to increase the likelihood of a successful attack or improve efficiency in data processing or speed of data retrieval, all of which are outside its intended purpose. Defense in depth is specifically about enhancing security robustness by complicating the attacker's path.