What is a Firewall?

The term "firewall" illustrates a system that protects a network and the machines on them from various types of attack. Firewalls are geared towards keeping the server up all the time and protecting the entire network.The primary goal of a firewall is to implement a desired security policy; controlling access in both directions through the firewall, and to protect the firewall itself from compromise. It wards off intrusion attempts, Trojans and other malicious attacks.Personal Firewalls:They are meant for the home user in a networked environment. They aim to block simple attacks, unlike the enterprise level firewalls that the corporate world uses at the server or router end. There are many ways to implement a firewall, each with specific advantages and disadvantages.Are they really needed?Nowadays organizations and professionals use Internet technology to establish their online presence and showcase their products and services globally. Their endeavor is to leverage digital technology to make their business work for them.All the organizations and professionals are shifting from Dialup to broadband and getting a fixed IP. It has led to an increase in security attacks, bugs in everyday working. This does not mean that Dialup being anonymous dynamic link or the firewall of the ISP network make you pretty safe.Now if your machine was under attack, you must have wondered what went wrong making your system crash suddenly. So I would rather like to say, it’s not necessary for anyone to actually know about you or your IP address to gain access to your system.If you system is infected or prone to intrusions, then beyond the anonymity of your Dialup connection or a dynamic IP, your system can be hacked.Types of AttacksIntrusion:There are many ways to gain unauthorized access to a system. Operating system vulnerabilities, cracked or guessed passwords are some of the more common. Once access is attained, the intruder can send email, tamper with data, or use the system privileges to attack another system.Information Theft and Tampering:Data theft and tampering do not always require that the system be compromised. There have been many bugs with FTP servers that allow attackers to download password files or upload Trojan horses.Service Attacks:Any attack that keeps the intended user from being able to use the services provided by their servers is considered a denial of service attack. There are many types of denial of service attacks, and unfortunately are very difficult to defend against. "Mail bombs" are one example in which an attacker repeatedly sends large mail files in the attempt at filling the server’s disk filesystem thus preventing legitimate mail from being received.Types of AttackersJoyrider:Not all attacks on computer systems are malicious. Joyriders are just looking for fun. Your system may be broken into just because it was easy, or to use the machine as a platform to attack others. It may be difficult to detect intrusion on a system that is used for this purpose. If the log files are modified, and if everything appears to be working, you may never know.Vandals:A vandal is malicious. They break in to delete files or crash computer systems either because they don't like you, or because they enjoy destroying things. If a vandal breaks into your computer, you will know about it right away. Vandals may also steal secrets and target your privacy.“In an incident a Trojan was being used to operate the web cam. All the activities being done in the house were being telecasted on the websites.”Spies:Spies are out to get secret information. It may be difficult to detect break-ins by spies since they will probably leave no trace if they get what they are looking for.A personal firewall, therefore, is one of the methods you can use to deny such intrusions.How Firewalls work?Firewalls basically work as a filter between your application and network connection. They act as gatekeepers and as per your settings, show a port as open or closed for communication. You can grant rights for different applications to gain access to the internet and also in a reverse manner by blocking outside applications trying to use ports and protocols and preventing attacks. Hence you can block ports that you don’t use or even block common ports used by Trojans.Using Firewalls you can also block protocols, so restricting access to NetBIOS will prevent computers on the network from accessing your data. Firewalls often use a combination of ports, protocols, and application level security to give you the desired security.