As we know, every computer connected to the Internet, or any other computer network, be they home networks or business networks, is likely to be the victim of an attack by a hacker.
The methodology generally used by the hacker is rake the network, sending data packets randomly in search of a online computer, and then look for a “hole” in the system security, which used to access the data that there is found.
This threat is even greater if the computer is permanently connected to the Internet. The reasons are several:
- The target PC can be connected without being constantly monitored
- The target PC is generally connected using broadband
- The target PC does not change (or very little) the IP address
Therefore, it is necessary that business networks and internet users that have a cable or DSL connection, protect the system from intrusions by installing a protection device. At this point comes in action the Firewall.
What is a firewall?
A firewall basically is a system that protects a computer or computer network from intrusions coming from a third network, specifically from Internet.
The firewall is a system that allows filtering data packets that walk the network. It is a “narrow bridge” that filters at least traffic between internal and external network.
A firewall can be a program (software) or computer (hardware) that acts as an intermediary between the local network (or local computer) and one or more external networks.
Operating a Firewall system
A firewall system contains a set of predefined rules that allow:
- Authorize a connection (allow)
- Lock a connection (deny)
- Redirect a connection request without informing the issuer (drop)
All these rules can install a filtration method that depends from the security policy adopted by the organization. Two types of security policies that allow commonly distinguished:
- Allow communications only explicitly authorized: “Everything that is not explicitly authorized is prohibited”.
- Prevent any communication was explicitly prohibited.
The first method is the safest, but it requires a precise definition of the communication needs of the entire network.
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