Which one of the following is a computer security device ?

A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It establishes a barrier between a trusted internal network and untrusted external networks, such as the Internet, to prevent unauthorized access and cyberattacks.

• Modem: A device that modulates and demodulates signals for data communication over telephone lines or cables.
• Compiler: A software tool that translates high-level programming code into machine language all at once before execution.
• Interpreter: A software tool that translates and executes programming code line-by-line.

While firewalls can be implemented as hardware, software, or both, they are fundamentally categorized as security devices/systems in computing.