Monitor Internet traffic flowing via my MacBook? My MacBook is connected to an Internet cable and meanwhile sharing the Internet connection with other devices over Wi-Fi. That is, my MacBook serves as a router, which broadcasts Wi-Fi signals.

Since essentially, all the Internet packets travel through my MacBook, there must be a way whereby I can monitor which device is viewing what contents using my hot spot.

Is there a software (preferably free) or some built-in block that allows me to achieve this?
You might want to look at the terminal command tcpdump as it will show all the traffic passing over your network. You have to run it via sudo but it should give you what you want.

sudo tcpdump -vv -i en0


Should show everything over your ethernet port.