What is the purpose of a Firewall?
Firewalls are absolutely vital for keeping network security in force. The firewall stops and controls the traffic that comes between your network and the different sites you go to. A firewall is a constituent of a company’s network protection, and it acts to keep in force the network security policy. It can log inter-network activity with efficiency. It can also reduce a network’s vulnerability. Whenever an organization is connected to the Internet but is not using a firewall, any host on the network has direct access to all resources on the internet. If you don’t have a firewall, every host online can attack every host in your network.
What a Firewall Cannot Do
Firewalls can’t always detect malicious data. For the most part they cannot offer any protection against an attack from inside, although they may log network activity should the criminal use the Internet gateway. A connection that doesn’t go through a firewall cannot be protected by a firewall. To put it another way, if you connect directly to the internet via modem, there is no way the network firewall can protect you. Some firewalls cannot protect from viruses. Firewalls also cannot totally protect against previously unknown attacks; while a simple firewall provides little protection against computer viruses.
Firewall User Authentication or Verification
All that user authentication implies is a means of establishing as valid or verifying the claimed identity. Usernames and passwords furnish this verification, however this is not very powerful user authentication. If a connection is not private, like an Internet hook-up that lacks encryption, usernames and passwords may be duplicated and replayed. Strength in terms of user authentication necessitates the utilization of encryption, like SSL certificates. These certificates stop ‘replay attacks’ from occurring, for instance when a username and password are obtained and ‘replayed’ for purposes of admittance or accessibility.
Firewall-to-firewall encryption
A connection that is encrypted is sometimes called a VPN, or Virtual Private Network. Cryptography makes this more or less private. Of course it isn’t really private. The information may be private but it is sent on a public network — the Internet. While VPNs were available before firewalls were, they became more common when they began running on firewalls. Today, most firewall vendors offer a VPN option.
Further firewall uses
* They are used often for content screening devices. Virus scanning is a possible addition to a firewall in this area. This is really a waste of resources, though, because virus scanning still must be performed on each individual station. The reason for this is that data may be introduced to the desktops from paths other than through the firewall. For example, individual users may bring in removable disks.
* URL screening: Logical additions to a firewall would be content screening and firewall controlled access to the web. One bad thing about using a firewall to screen content or URLs is that it causes degraded performance.
* To limit the bandwidth that any one person or specific service in the network can use below a certain maximum.
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