A datacenter recently experienced a breach. When access was gained, an RF device was used to access an air-gapped and locked server rack. Which of the following would BEST prevent this type of attack?

A Faraday cage is an enclosure designed to block electromagnetic fields, including radio frequencies, by containing them within or preventing them from entering. Placing a Faraday cage around the server rack or the entire secure area would effectively prevent an RF device from communicating with the air-gapped servers, thereby blocking the attack vector described.

Smart cards are used for authentication for logical or physical access and do not prevent external RF devices from communicating with servers.

Infrared detection senses motion or heat to alert to physical presence but does not block or prevent RF communication from an external device.

Alarms provide notification of security events but are a detection and response control, not a preventive measure against RF communication itself.