Network firewalls get the name from physical walls which prevent fire spreading from one section of a building to another. In these walls are structures which strictly control access from one side to another and in this case it is another form of Pc security.
That's exactly what a network-firewall does it restrict the flow of data and program instructions in or out of a system that are on a LAN (Local area network).There are two basic types of these walls one is hardware and the other is software, though the distinction can be misleading. Hardware rarely does much without extra software to guide it, and software can't even exist without hardware. It has to be stored somewhere and execute on something.
Hardware protective walls are commonly used between networks — for example between a corporate network and the Internet. The Internet is nothing more than a large set of mutually cooperating networks. Incoming traffic from the Internet is restricted to public access areas or to particular computers on the corporate network. Computers in the corporate network 'behind' the protective wall and anti-spam-firewall and spam blocker access each other and the Internet.Internal protective walls within corporate networks are also used, typically to keep resources restricted to certain groups, or to prevent viruses infecting some groups from spreading to others.
Software or 'personal' firewalls along with anti-spam-firewall and spam blockers are more often used in Pc security that connects to the Internet. They're slower than hardware walls, which are specialized for that function, and they use resources on the individual's PC.
These protective network walls help prevent unauthorized access to systems by hackers or viruses. They control both inbound and outbound traffic according to a 'policy' established when the wall is installed, or later configured. The policy determines which programs can access the Internet and what kind of incoming or outgoing traffic is allowed.
Browsers, e-mail programs and some auto-updating programs (such as antivirus software) all require network access. A personal firewall can be set up to allow this kind of traffic, while disallowing others and the same can be down with anti-spam-firewalls.
Through these walls can 'learn' which programs can access the Internet freely by scanning the network. The first time a program tries to connect to the Internet the protective wall signals an alert. The user modifies the protective wall policy by (dis)allowing that particular program to access the Internet. The rule of thumb is: if you don't recognize the program, don't allow access. Most installation software will specify what protective settings are needed for the wall to run common programs properly.
Hackers routinely scan computer networks looking for open 'ports' (numbers used by network software to distinguish traffic) through which they can gain access to your computer. Ports are individual entry connection points between the computer and the Internet. If a hacker can find an open port or there is no Pc security, it can be used to transmit a worm carrying a payload which can give the hacker control over your computer. These protective walls can close all unused ports.The best personal-firewalls not only close ports, they hide their very existence. This means a hacker program scanning for open ports won't receive a reply to scan requests, rendering the system 'invisible'.
That doesn't mean, unfortunately, that personal protective walls and spam blockers and anti-spam-firewalls are invulnerable. Unlike hardware walls, personal protective walls are part of the computer system — they're just another program — and are just as vulnerable to virus attacks as any other. Some viruses target these program walls by modifying the policy file. If this happens your computer may become vulnerable to hackers even when you thought the Pc security was secure.
Nevertheless, connecting to the Internet without using a firewall is ill-advised. Open ports are a vulnerability that can be easily exploited by hackers. To protect your system integrity be diligent about scanning incoming files for viruses, by using antivirus software and avoiding unexpected e-mail attachments.
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Windows Registry 101 Windows Registry 101 - The basics and tips for Windows or Vista Registry
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Anti-spam firewall what it can do for you Anti-spam firewall how it can help protect you from programs that attack your computer
Firewall the best ways to protect your computer return to Business computing guide