Overview of Firewall Technology

A computer firewall acts in much the same way a physical firewall does. A firewall will keep dangerous attacks from reaching your computer.There are two main types of firewalls for computers: software and hardware. Hardware firewalls are normally used to protect entire networks of computers while software firewalls are typically used on one computer and usually protect only that computer.

How Firewalls Work
A firewall works by blocking outside computers from accessing certain resources on the computer being protected. These resources are located at individual "ports." By sealing ports from being accessed by other computers, the firewall can regulate if the computer can be contacted, or if the attempts will be denied.


What a Firewall can Protect Against
Firewalls will protect against active attempts to breach your computer's security. Good firewalls will also gather evidence of hacking attempts, allowing the administrator to pursue legal action if so desired.For a network administrator, firewalls provide a single point where security to the outside can be managed and audited. A firewall can serve the same purpose on a network as a locked gate does to a physical location.


What a Firewall Cannot Protect Against
A firewall cannot protect your computer against attacks that do not use the network. This means that the firewall is not an Anti-Virus program. You must have a good Anti-Virus program installed to prevent infection from viruses. Firewalls will also not protect against traffic that is configured to let through to the computer. If you open port 80 (for a web server), the firewall will let all traffic through on that port. Some firewalls can still be configured to scan for possible attacks in traffic that is being let through, but it is still best to make sure your programs are secured before outside users are allowed to access them. Firewalls are still important to have in blocking ports. If an older Anti-Virus program (or lack of an Anti-Virus program) allows a trojan horse to install itself on your computer, a firewall can block malicious hackers from accessing the trojan to connect to your computer, unless you specifically open the port the trojan uses.


I use an Anti-Virus Program, Do I Still Need A Firewall?
Although an anti-virus program is important, it will not protect your computer from a malicious hacker actively scanning for a hole in your security. A good firewall will prevent this scanning from occurring - effectively 'hiding' your computer from malicious hackers. A firewall will also help protect your computer by blocking ports that a trojan horse (that managed to slip by the Anti-Virus program) uses.


I Connect Through A Modem, Do I Really Need A Firewall?
Firewalls are not just for large companies. While it is essential for users connecting through DSL or Cable Modem, dialup modem users should also be very concerned. Even users who connect over dialup modem connections may have security holes in the software they use. Hackers know this and will also target modem users. If you use any sort of Internet program, like ICQ, and if these applications have security flaws, a malicious hacker could take control of the user's computer. A hardware firewall is not necessary, but a personal firewall is highly recommended.