Firewalls: Sources

Rao, Umesh Hodeghatta, and Umesha Nayak. "Chapter 10: Firewalls." The InfoSec handbook: An introduction to information security. Springer Nature, 2014, pp. 205-223. URL: https://link.springer.com/content/pdf/10.1007/978-1-4302-6383-8.pdf#chapter+10:+firewalls

Salomon, David. "Chapter 7, Section 6: Firewall Basics." Elements of computer security. Springer Science & Business Media, 2010, pp. 202-205. URL: https://link-springer-com.brooklyn.ezproxy.cuny.edu/content/pdf/10.1007/978-0-85729-006-9.pdf#7.6+firewall+basics