The rapid scientific and technological progress, leads to a constant emergence of new words or meanings of others already known, that in a few years have taken hold in the specific discipline, in which they appeared. However, the unexpectedly rapid spread of the term "Firewall" and its recent entry as a defense device for a personal computer or private network against attacks from outside it not usual.
In computer terms a firewall is a program that can be resident on the machine itself or another, and its function is to protect the network or equipment outside incursions, whether automatic or manual. The disadvantage of a firewall is that while providing protection, it also requires knowledge and complicates the traffic and activity of the various programs normally used in case the user does not configure them properly.
A firewall is the basic mechanism of intrusion prevention against external threats. Its main functions include access control (both input and output), user authentication, event logging, auditing and generating alarms.
Personal firewalls are programs that are installed by a resident in our computer and that filter and control the network connection. They are not recommended for inexperienced users and that can block needed programs (even the very possibility of browsing the Internet).
Installing a firewall also requires a process of "training to use". It is normal for our Personal Firewall to ask us if we give permission to other network programs as we use them. This at first can be tricky or even annoying.
A personal firewall does not prevent the infection with Trojans, viruses and worms of our system. We should also have a good antivirus, one of the best antivirus software if it is possible, that should be updated and properly configured.
In general, along with an antivirus what to expect from a Personal Firewall are the following: To protect your system from unauthorized access over the Internet. The ability to alert us of intrusion attempts and also the ability to maintain a registry to follow their tracks. The capacity to block dangerous content on the Internet: Java applets, ActiveX controls, cookies, etc. Application-level filtering for connections to the outside (used by Trojan horses).