Explanation/Reference:
Explanation:
While the other answers are all steps in moving from normal operations to maintenance mode, we do not necessarily initiate any enhanced security controls.

Fences are physical controls; carpets and ceilings are architectural features, and a door is not necessarily a control: the lock on the door would be a physical security control. Although you might think of a door as a potential answer, the best answer is the fence; the exam will have questions where more than one answer is correct, and the answer that will score you points is the one that is most correct.

Explanation
An intrusion detection system (IDS) is designed to analyze network packets, compare their contents or characteristics against a set of configurations or signatures, and alert personnel if anything is detected that could constitute a threat or is otherwise designated for alerting.

XML firewalls are most commonly deployed in line between the firewall and application server to validate XML code before it reaches the application.