CompTIA Exam CS0-001 Topic 2 Question 17 Discussion

A company Installs ICS devices to manage the building's lighting controls. The network administrator places the controllers on a VLAN segment of the company's network After a month, senior management reports someone has been modifying the lights on the building floors after hours to spell words on the building. The security administrator Is tasked with resolving the Issue Immediately and stopping access to the ICS devices. Which of the following Is the BEST method to quickly secure the devices for controlling the lights at minimum cost to the company?