Firewall is an integrated collection of security measures designed to prevent unauthorized electronic access to a networked computer system. It is a devices configured to permit, deny, encrypt, decrypt, or proxy all computer traffic between different security domains based upon a set of rules and other criteria.
A firewall is a hardware or software solution to enforce security policies.A barrier in a network that will only pass packets authorized to reach the other side.
A method of protecting one network from another network. A firewall blocks unwanted access to the protected network while giving the protected network access to networks outside of the firewall.
A firewall is a dedicated appliance, or software running on another computer, which inspects network traffic passing through it, and denies or permits passage based on a set of rules.
Network security barrier. A firewall is a device that guards the entrance to a private network and keeps out unauthorized or unwanted traffic. When people talk about a corporate or enterprise firewall, they normally assume a series of devices guarding all points of entry, thus creating a secure environment "behind" or "inside" the firewall.