3 to 4 high fencing is considered minimal
protection, only for restricting casual trespassers. Answers "6 to 7 high" and "8 to 12 high"
are better protection against intentional intruders.

Preventive Technical Controls are the technical ways of restricting who or what can access system resources and what type of access is permitted. Its purpose is to protect the OS and other systems from unauthorized modification or manipulation. It is usually built into an operating system, or it can be a part of an application or program, or an add-on security package, or special components to regulate communication between computers. It also protects the integrity and availability by limiting the number of users and/or processes. These controls also protect confidential information from being disclosed to unauthorized persons.

Section: Security Operations