A firewall for computer networks is much like a real firewall that stops fire from spreading from one part of a building to another part. A firewall will control and limit access from one side to the next.
A computer firewall works in the same way as a physical firewall does. It limits the movement of data and programs to and from a computer system.
Firewalls for hardware are often used between computer networks, such as between the Internet and a company network. The Internet is a complex system of networks that all cooperate together. Internet traffic that is incoming is restricted to access areas that are public or to certain computers on the company network. Company network computers are “behind” the firewall and can access other network computers as well as the Internet.
Some companies also use internal network firewalls so that certain resources are limited to certain computer groups. Internal firewalls are also used to prevent viruses from spreading through the network.
Personal firewalls, which are software firewalls, are often used in PC computers that are connected to the Internet. A software firewall will be slower that a hardware firewall which has been specialized for just that type of function. They also use some of the resources on the PC.
A firewall can prevent or limit access to computer systems by viruses or hackers. It will manage both outbound traffic and inbound traffic when a policy is put into place at the time the firewall is installed. These policies can also be configured later and will determine what programs are allowed access to the Internet as well as which traffic is allowed in and out of the system.
Network access is required by email programs, antivirus software, and Internet browsers. Personal firewalls can be put in place that allow some of this Internet traffic while disallowing others.
A firewall is smart enough to know which programs are allowed access to the Internet and which are not. When a program first tries to get on to the Internet the firewall will signal the user. The user will either deny access or will modifiy the policy for the firewall to allow access. The thing to remember is that if you don’t recognize a certain program you shouldn’t give it access. Most software that you install will let you know what firewall settings you need to set so that the program can run correctly.
Hackers will search through computer networks for ports that are open so that they can get into your computer. A port is an entry point between your computer and the Internet. When a hacker finds an open port they will use this port to send a worm which is carrying a payload to give the hacker complete control over the PC. Firewalls are used to close any ports that aren’t being used.
Accessing the Internet without using a firewall is not advised. Always keep in mind that open ports will be vulnerable to hackers. You need to protect your firewall diligently so that incoming data and files are scanned for viruses. You should also avoid opening up email attachments that you aren’t expecting.