What Firewalls Can Do
One of the main functions of firewall is to examine application or protocol that tries to establish a communication channel on your computer in both directions - inbound and outbound. Firewall program will alert you every time a program tries to establish suspicious or illegal connection to or from your computer and allow access you initiated.
Port scanners are program use to scan target computers or machines for open ports (something your home doors or windows) that they can use to access your computer It is very important that you firewall able to block or stop them.
When malicious program such spyware, Trojan Horse or worms on your computer, the firewall can prevent them from establishing outbound connection to other computer in the Internet. This is necessary to prevent any information to be sent from your computer to the creator of the malicious program or vice versa
What Firewalls Can’t Do
Firewall cannot protect Internet attack that uses common ports and applications. Web and e-mail application uses ports 80 and port 110 as the point of communication will allow to pass by the firewalls. The firewall will be helpless if a malicious program hide in the attachment of the e-mail. Other web sites embed with malware, which will load itself to your computer what your browser access to that site.
Lastly, which probably that is you, who contribute one of the weakest links that, allow it to happen, all firewalls do only you tell them to do. If a firewall asks you whether you want to allow a specific program to run or access the Internet, and you say yes, and that program turn out to be malicious, good luck to you.
Knowing what firewalls can do and can’t do able you to understand this application strong points and the weak ones, and also give you some idea how to handle malware and how it works. As the Internet mature, so do the "bad people" that lurk in cyberspace. Installing firewalls alone may not enough to keep tech-savvy crooks at bay. You also need other security software in your computer to combat against other security threats like spyware and viruses