Conceptually, there are two types of firewalls:

1. Network Level

2. Application Level

They are not as different as you might think, and latest technologies are blurring the distinction to the point where it’s no longer clear if either one is “better” or “worse.” As always, you need to be careful to pick the type that meets your needs.

Network level firewalls generally make their decisions based on the source, destination addresses and ports in individual IP packets. A simple router is the “traditional” network level firewall, since it is not able to make particularly sophisticated decisions about what a packet is actually talking to or where it actually came from. Modern network level firewalls have become increasingly sophisticated, and now maintain internal information about the state of connections passing through them, the contents of some of the data streams, and so on. One thing that’s an important distinction about many network level firewalls is that they route traffic directly though them, so to use one you usually need to have a validly assigned IP address block. Network level firewalls tend to be very fast and tend to be very transparent to users.

[Screened host firewall]

Example Network level firewall: In this example, a network level firewall called a “screened host firewall” is represented. In a screened host firewall, access to and from a single host is controlled by means of a router operating at a network level. The single host is a bastion host; a highly-defended and secured strong-point that (hopefully) can resist attack.

[Screened subnet firewall]

Example Network level firewall: In this example, a network level firewall called a “screened subnet firewall” is represented. In a screened subnet firewall, access to and from a whole network is controlled by means of a router operating at a network level. It is similar to a screened host, except that it is, effectively, a network of screened hosts.

Application level firewalls generally are hosts running proxy servers, which permit no traffic directly between networks, and which perform elaborate logging and auditing of traffic passing through them. Since the proxy applications are software components running on the firewall, it is a good place to do lots of logging and access control. Application level firewalls can be used as network address translators, since traffic goes in one “side” and out the other, after having passed through an application that effectively masks the origin of the initiating connection. Having an application in the way in some cases may impact performance and may make the firewall less transparent. Early application level firewalls such as those built using the TIS firewall toolkit, are not particularly transparent to end users and may require some training. Modern application level firewalls are often fully transparent. Application level firewalls tend to provide more detailed audit reports and tend to enforce more conservative security models than network level firewalls.

[Dual-Homed Gateway]

Example Application level firewall: In this example, an application level 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 level firewalls and application level firewalls. It is likely that network level firewalls will become increasingly “aware” of the information going through them, and application level 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.

https://www.bestitdocuments.com/Samples