Answer:
It is a device installed at the boundary of an incorporate to protect it against the unauthorized access.
Explanation: A firewall can be the type of either a software or the hardware device that filters each and every data packet coming from the network, internet. It can also be considered as a device installed at the boundary of an incorporate to protect form unauthorized access. Sometimes firewall also refers to the first line of defense against viruses, unauthorized access, malicious software etc.