What device connects multiple devices on a network and broadcasts data to all connected devices?

The device that connects multiple devices on a network and broadcasts data to all connected devices is a hub. A hub operates at the physical layer of the OSI model and functions as a simple networking device that receives data packets from one device and sends them to all other devices connected to the hub. This means that when a device sends data to the hub, the hub does not differentiate between the devices; it simply transmits the data to all connected devices regardless of the intended recipient. This characteristic can lead to increased network traffic and potential data collisions, as all devices receive the same data simultaneously.

In contrast, other options like a router and a switch provide more advanced functions. A router connects different networks and intelligently routes data packets based on their destination addresses, while a switch operates at the data link layer and can direct data to specific devices based on their MAC addresses, minimizing unnecessary traffic. A firewall, on the other hand, is primarily used for network security, filtering incoming and outgoing data based on predetermined security rules. Thus, while these devices play critical roles in networking, a hub specifically embodies the characteristic of broadcasting data to all devices, making it the correct answer for this question.