Page 167 - DCAP516_COMPUTER_SECURITY

Unit 13: Firewalls

Notes
Figure 13.6: Dual Homed Gateway

Example: Application Layer Firewall
In Figure 13.6, an application layer firewall called a “dual homed gateway’’ is represented. A
dual homed gateway is a highly secured host that runs proxy software. It has two network
interfaces, one on each network, and blocks all traffic passing through it.

The Future of firewalls lies someplace between network layer firewalls and application layer
firewalls. It is likely that network layer firewalls will become increasingly “aware’’ of the
information going through them, and application layer firewalls will become increasingly
“low level’’ and transparent. The end result will be a fast packet-screening system that logs and
audits data as it passes through. Increasingly, firewalls (network and application layer) incorporate
encryption so that they may protect traffic passing between them over the Internet. Firewalls
with end-to-end encryption can be used by organizations with multiple points of Internet
connectivity to use the Internet as a “private backbone’’ without worrying about their data or
passwords being sniffed.

13.3.3 Circuit-Level Firewalls

These applications, which represent the second-generation of firewall technology, monitor TCP
handshaking between packets to make sure a session is legitimate. Traffic is filtered based on
specified session rules and may be restricted to recognized computers only. Circuit-level firewalls
hide the network itself from the outside, which is useful for denying access to intruders. But they
don’t filter individual packets.

13.4 Firewall Configuration

Today’s Internet is a dangerous place for your computer; there’s just no denying it. A few years
ago you could happily go about your business on the web without any form of protection, and
still face only a slim chance of being virus infested, hacked or otherwise interfered with. These
days it’s practically impossible. There are vast amounts of viruses and malware infections
moving through the Internet daily, many of which need no prompting or permission to infect
an unprotected computer.
To prepare yourself for today’s Internet environment, you need the holy trinity of computer
security: effective antivirus/anti-spyware software, regular updates and a firewall.

LOVELY PROFESSIONAL UNIVERSITY 161