I want to ask who assigns the IP address to a machine that connects to
the Internet? The ISP, the network card (i.e. MAC address??), or the
router?

It seems like my IP address is fixed everytime connected to the
Internet, it seems very unsecure because it allows hackers track the
computers more easily.

I thought the IP address should be dynamic, and each time when we
connect to the Internet should have different IP address.

Is there a way that makes the IP address in my machine becomes dynamic?

Please advise. thanks!!