CompTIA Security Plus Mock Test Q143

A technician has just installed a new firewall onto the network. Users are reporting that they cannot reach any website. Upon further investigation, the technician determines that websites can be reached by entering their IP addresses. Which of the following ports may have been closed to cause this issue?

A. HTTP
B. DHCP
C. DNS
D. NetBIOS

Correct Answer: C
Section: Network Security

Explanation:
DNS links IP addresses and human-friendly fully qualified domain names (FQDNs), which are made up of the Top-level domain (TLD), the registered domain name, and the Subdomain or hostname. Therefore, if the DNS ports are blocked websites will not be reachable.

Incorrect Answers:
A: HTTP is responsible for the transmission of HTML documents and embedded multimedia components.
B: Dynamic Host Configuration Protocol (DHCP) allows DHCP servers to assign, or lease, IP addresses to computers and other devices that are enabled as DHCP clients.
D: NetBIOS is a program that allows applications on different computers to communicate within a local area network (LAN).

References:
Stewart, James Michael, CompTIA Security+ Review Guide, Sybex, Indianapolis, 2014, pp. 42, 46
https://technet.microsoft.com/en-us/library/cc896553(v=ws.10).aspx
http://en.wikipedia.org/wiki/NetBIOS