A firewall is necessary because it blocks unauthorized access to private networks, safeguarding them from hackers, viruses and worms. A firewall works by monitoring all messages entering and leaving the intranet and restricting those that do not meet security data. A firewall can take the form of hardware, software or a combination of both. Some of the most common forms are packet filtering, circuit-level gateway implementation and web application firewalls.
Hackers, viruses and other online threats put computer users at risk of information theft and jeopardized computer performance. A firewall acts as the first line of defense against these threats. It checks network traffic and connections but does not authenticate individual users for access to a network.
In packet filtering, the system examines the packets that enter and leave the network. User-defined rules determine whether access is granted or declined. Packet filtering is susceptible to IP spoofing, the creation of IP packets with a forged IP address.
Circuit-level gateway implementation applies security mechanisms whenever a TCP or UDP is established. Upon authentication of a connection, packets flow between hosts without further revision.
A web application firewall is a hardware filter, such as a sever plug-in, that applies a pre-formulated set of rules to a HTTP conversation, thereby identifying and blocking attacks from malevolent sources.