A firewall is placed between private networks such as LAN/WAN and external network, Internet. The role of firewall is to control access to internal sought by the user. The user may be an employee, visitor, supplier, customer or a person not related to the organization. Firewall processes names, Internet protocol (IP) addresses, applications, and all incoming requests and confirms the authenticity and validity of the access by checking against access rules programmed into the system. The basic advantage of firewall is that it prevents unauthorized communication controlling the security threat to company‘s network.
There are essentially two types of firewall technologies one is ‗proxy‘ and other is ‗packet‘. In packet technology, firewall scans each packet of incoming communication verifies the source and addressed to whom. Then it sets up state tables out of the package and cross checks with the user defined rules to make a decision on permission to enter the network.
Proxy firewall stops data originating from outside, checks for the access rules, and pass a ‗Proxy‘ of it to the network. Proxy is an application which acts as intermediary between private network and Internet to control the traffic. Proxy firewall needs programming work, system resources but is safer to a great extent to contain the threat of unauthorized access.
In additional to firewall systems, software tools are available that can be installed at locations where sensitive data and information are stored. This software scans the identity references of the user before access is given to the location. The use of such software tools at a few sensitive locations is second additional control after firewall check.
If checking response is negative, access is denied or location is switched off for work and network, an administrator is communicated to look into the incidence. The software solution is called Intrusion Detection System.
Firewall is made up of computers and software. A firewall can be a communication processor, known as router, or a dedicated server along with software written for checking, verification and decision making for allowing or disallowing the access. Firewall checks network traffic for passwords, security codes and access rights before any decisions are made. A corporate network can have more than one firewall installed at various locations.