When using the Internet, whether as an individual or as a company, we want the files on your computer to be safe. That no one from the outside could break into them, but also we do not want them to leak outside. One way to protect your computer is a firewall. Firewall is a computer equipment (hardware) or software blocking unwanted and unauthorized access to the computer.

It filters all incoming and outgoing connections (also for the internal LAN, in front of which it stands) and denies the access requests that it considers to be threatening  to the computer. To do this it uses specific techniques such as: the introduction of user identification algorithms (password, digital certificate); checking the origin of incoming packets and accept only those desired (e.g. SPI); or protecting programs serving only some protocols (e.g. FTP).

Another important function of the "firewall" is preparing logs, so the register of all the major events within the network. This allows you to find in the past the moment when the problem occurred, and thus track the "offender". There are different types of firewalls. Filtering firewalls, which usually work also as a router, monitor the flow of packets and act as a kind of "sieve", which passes only this, which is allowed by our settings. More advanced filtering firewalls also allow you to use many other features, such as anti-virus protection.

Masking firewalls also called network address translation (NAT) changes the internal host's IP address, so you can hide it from the outside monitoring. Intermediate firewall (called "proxy"), connects with the server, domain, site, on the user’s behalf. The session with the firewall starts on the remote Web server, and from there it is sent to us. This not only allows to filter the content of the sites in terms of malware and viruses, but also to manually set the limits.

This enables us to block porn sites so that the children do not have the access to them, or to block popular pages to our lawyers that they have the access to the Internet, but do not waste time. Properly configured, "firewall" should repel all known types of virtual attacks.