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Last Updated: Sep 2009
Last Updated: Sep 2009
There are a number of technologies employed by firewalls to protect your data and network, the first is a simple set of rules, this permission based scheme plugs the holes that windows operating systems are sadly renowned for. Your windows operating system is like a Swiss cheese with many holes in it, some must remain for applications like email and web browsing to get to the public internet but windows ships with many other holes or "ports" open as standard.
For example many home machines will never network with another machine in their entire life, but as standard they ship with the NetBIOS ports open, there are a number of viruses and hacking tools that exploits this simple fact and there is an equally frightening number of home PC's sat right now with this ort wide open.
A simple rule set starts from the position of all ports (or doors) closed and then as you start each application you have to create a rule to let it get to the internet or network, most firewalls will come pre configured to allow internet and pop3 email access from start-up but you'll find that instant messaging systems like MSN messenger and yahoo IM will need permission to work.
This guest list a bit like a bouncers VIP list is maintained by you either as an administrator on the top of the range systems or on a simple software system it will prompt you each time a new programme asks for access.
There are 2 physical types of firewall software and hardware.
Software firewalls are commonly used in the home environment big names like Norton and MacAfee both make and sell internet personal firewalls, these do a good job of providing a basic rules based protection system by running an application on your PC.
Hardware firewalls are more common in the business environment where dedicated units have the outside world plugged in onside and the trusted network on the other, these are often supplied as a pair so that failure of a unit does not make the network vulnerable.
Both hardware and software firewalls use a number of different techniques to keep your PC and network safe, the first systems already described is a rules based or packet filter system, here all data incoming and outgoing is inspected to see that is coming from and going to trusted ports on the system and possibly even trusted IP addresses.
The next level up is a proxy server, this stands between the outside internet and the trusted network it intercepts all packets of data and checks if they meet the packet filter rules before forwarding data to the machine inside the trusted network. This adds a level of security by never letting the internet machine talk directly with the trusted machine, a system of network address translation (NAT) hides your internal IP address from the internet meaning all data has to go through the firewall for inspection. A proxy server is very good against brute force attacks], the equivalent of someone trying to shoulder charge your door down, its like putting an extra set of doors between your machine and the attack.
The best level of firewall technology is normally found only in high end firewalls but is slowly creeping into the top end home devices, SPI or stateful Packet Inspection, this not only applies rules to incoming data it checks various security protocols and can determine if data is really from whom it claims to be, this is in effect a smart firewall which is looking for known characteristics of certain attacks and spoofing attempts.
Most firewalls use at least 2 of these techniques and the best firewalls are a combination of all 3, plus most corporate firewalls use a combination of hardware and software to protected their networks.
For example many home machines will never network with another machine in their entire life, but as standard they ship with the NetBIOS ports open, there are a number of viruses and hacking tools that exploits this simple fact and there is an equally frightening number of home PC's sat right now with this ort wide open.
A simple rule set starts from the position of all ports (or doors) closed and then as you start each application you have to create a rule to let it get to the internet or network, most firewalls will come pre configured to allow internet and pop3 email access from start-up but you'll find that instant messaging systems like MSN messenger and yahoo IM will need permission to work.
This guest list a bit like a bouncers VIP list is maintained by you either as an administrator on the top of the range systems or on a simple software system it will prompt you each time a new programme asks for access.
There are 2 physical types of firewall software and hardware.
Software firewalls are commonly used in the home environment big names like Norton and MacAfee both make and sell internet personal firewalls, these do a good job of providing a basic rules based protection system by running an application on your PC.
Hardware firewalls are more common in the business environment where dedicated units have the outside world plugged in onside and the trusted network on the other, these are often supplied as a pair so that failure of a unit does not make the network vulnerable.
Both hardware and software firewalls use a number of different techniques to keep your PC and network safe, the first systems already described is a rules based or packet filter system, here all data incoming and outgoing is inspected to see that is coming from and going to trusted ports on the system and possibly even trusted IP addresses.
The next level up is a proxy server, this stands between the outside internet and the trusted network it intercepts all packets of data and checks if they meet the packet filter rules before forwarding data to the machine inside the trusted network. This adds a level of security by never letting the internet machine talk directly with the trusted machine, a system of network address translation (NAT) hides your internal IP address from the internet meaning all data has to go through the firewall for inspection. A proxy server is very good against brute force attacks], the equivalent of someone trying to shoulder charge your door down, its like putting an extra set of doors between your machine and the attack.
The best level of firewall technology is normally found only in high end firewalls but is slowly creeping into the top end home devices, SPI or stateful Packet Inspection, this not only applies rules to incoming data it checks various security protocols and can determine if data is really from whom it claims to be, this is in effect a smart firewall which is looking for known characteristics of certain attacks and spoofing attempts.
Most firewalls use at least 2 of these techniques and the best firewalls are a combination of all 3, plus most corporate firewalls use a combination of hardware and software to protected their networks.
A firewall is a system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.
A firewall is also called a Border Protection Device (BPD) in certain military contexts where a firewall separates networks by creating perimeter networks in a Demilitarized zone (DMZ). In a BSD context they are also known as a packet filter. A firewall's function is analogous to firewalls in building construction.
Proper configuration of firewalls demands skill from the firewall administrator. It requires considerable understanding of network protocols and of computer security. Small mistakes can render a firewall worthless as a security tool.
A firewall is also called a Border Protection Device (BPD) in certain military contexts where a firewall separates networks by creating perimeter networks in a Demilitarized zone (DMZ). In a BSD context they are also known as a packet filter. A firewall's function is analogous to firewalls in building construction.
Proper configuration of firewalls demands skill from the firewall administrator. It requires considerable understanding of network protocols and of computer security. Small mistakes can render a firewall worthless as a security tool.
