In this age of universal electronic connectivity of viruses and hackers, of electronic Eavesdropping and electronic fraud, there is indeed no time at which security does not matter. The explosive growth in computer systems and their interconnections via network has increased the dependence of both organizations and individuals on the information stored and communicated using these systems. This, in turn, has led to a heightened awareness of the need to protect the data and messages, and to protect systems from network based attacks. As we tend towards a more and more computer centric world, the concept of data security has attained a paramount importance. Though present day security systems offer a good level of protection, they are incapable of providing a "trust worthy" environment and are vulnerable to unexpected attacks. The generic name for the collection of tools design to protect data and to thwart hackers is computer security.
[...] A firewall provides a location for monitoring security related events. Audits and alarms can be implemented on the firewall system. A firewall convenient platform for several internet functions that are not security related. These include a network address translator, which maps to local address to internet address, and a network management function that audits or logs internet usage. A firewall serves as the platform for IP sec. HOW A FIREWALL WORKS Packets: When messages are sent along the internet, they are broken up into small ‘packets' that take different routes to get to the destination. [...]
[...] Security accepts come into play when it is necessary or desirable to protect the information transmission from an opponent who may present a threat to confidentiality, authenticity, and so on. All the techniques for providing security have two components: A security- related transformation on the information to be sent. Examples include the encryption of the message, which scrambles the message so that it is unreadable by the opponent, and the addition of code based on the contents of the message, which can be used to verify the identity of the sender. [...]
[...] At the very least, perimeter routers can be employed in two ways: either without packet filtering rules involved or by using an IP filtering router solution selectively passing or blocking data packets based on port information or addresses acceptable by the security policy. Of course, a firewall must always be situated next to the router. Some practical solutions to this are illustrated in Figures 1 and 2 below. Fig: Model network using firewall SHORT COMINGS OF A FIREWALL Firewall can't protect against attacks that don't go through the firewall. [...]
[...] Firewalls are tools that can be used to enhance the security of computers connected to a network, such as a LAN or the internet. A firewall separates a computer from the internet, inspecting packets of data as they arrive at either side of the firewall inbound to or outbound from the computer to determine whether it should be allowed to pass or be blocked. Firewalls act as guards at the computer's entry points (which are called ‘ports') where the computer exchanges data with other devices on the network. [...]
[...] There are a lot of organizations out there buying expensive firewalls and neglecting the numerous other back-doors into their network. For a firewall to work, it must be a part of a consistent overall organizational security architecture. Another thing a firewall can't really protect against is a traitor inside the network. While an industrial spy might export information through your firewall, he's just as likely to export it through a telephone. FAX machine, or floppy disk. An attacker may be able to break in to the network by completely bypassing the firewall, if he can find a helpful employee inside who can be fooled into giving access to a modem pool. [...]
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