What?
What is a firewall?
In computing, a firewall is a network security system that controls the incoming and outgoing network traffic based on an applied rule set. A firewall establishes a barrier between a trusted, secure internal network and another network (e.g., the Internet) that is assumed not to be secure and trusted.
Stand-alone firewalls exist both as firewall software appliances to run on general purpose or standard industry hardware, and as hardware-based firewall computer appliances.
Why?
Why is a Firewall required?
As a rule a Firewall is preventing that confidential traffic which takes place on the internal network is not publicly available.
A firewall should thus prevent unauthorized access to the internal network. Such a firewall called a network firewall. Typically, the firewall is not solely run on industry hardware.
Most firewalls have a web based interface, so they are easy to manage through a browser.
How?
How does a Firewall work?
A Firewall inspect all the traffic that goes through it, and it is its rules that determine whether the traffic is allowed or whether it should be rejected.
The simplest form of firewall is a packet filter. Each IP packet is inspected and will be either rejected or accepted. With this system, TCP-based traffic handled since sent a special synchronization packet (the SYN flag) which tells the establishment of a new connection. If this package is rejected, it can not establish a connection. A packet filter can also distinguish between sender or recipient addresses and reject or accept traffic on the basis of this information.
Who?
Who should use a Firewall?
All companies need if they have Internet access from their komputere if they have e-mail exchange.
All companies today have some form of Firewall, whether built into the router that came with the Internet connection or whether there is a dedicated software / hardware Firewall, and this should be correctly configured relative the company's needs.
A firewall is the first hurdle hackers meet, and therefore this must be of a certain standard, and must be able to shut down unwanted traffic.
Today there are many Firewall manufacturers in the market, and many of these are called UTM (Unified Threat Management) and Next Generation Firewall solutions as there are constantly found new ways to implement security at this level, this may for instance be that it has built-in E-mail scanner (RBL, Viruses, Spam, etc.), WAF (Web Application Firewall), VPN, and many other features.