ITPEC IP April 2023 Question 31
Which of the following is placed between an internal network and an external network in order to prevent unauthorized access from the external network to the internal network?
Explanation
Firewall — placed at the boundary between the internal network and the external network, it lets through only the traffic its rules permit.
A firewall checks the packets crossing it, such as their source and destination IP addresses and port numbers, against a rule set: permitted communication passes and everything else is blocked. Between the internal network and the Internet it stops unauthorised access from outside while internal users still reach the services they need. Servers the outside must reach, such as a public web server, are usually put in a DMZ, a separate segment behind the firewall, so the internal network itself stays closed.
Answer (d)
Why not others:
- •(a) DHCP server — automatically assigns IP addresses and other network settings to devices joining a network
- •(b) Search engine — a web service that indexes pages and finds them by keyword
- •(c) Switching hub — relays frames inside a LAN to the port of the destination MAC address; it connects devices but does not block access
Key rule: A firewall filters traffic at the network boundary by address and port rules; a DMZ holds the servers the outside must reach, keeping the internal network closed to it.
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