Selection criteria − It is a used as a condition and pattern matching for decision making.Īction field − This part specifies action to be taken if an IP packet meets the selection criteria. The decision can be based on factors other than IP header fields such as ICMP message type, TCP SYN and ACK bits, etc. Packet-filtering firewalls allow or block the packets mostly based on criteria such as source and/or destination IP addresses, protocol, source and/or destination port numbers, and various other parameters within the IP header. The firewall inspects and filters data packet-by-packet. In this type of firewall deployment, the internal network is connected to the external network/Internet via a router firewall. Stateless & Stateful Packet Filtering Firewall Modern firewalls have a mix of abilities that may place them in more than one of the three categories. These three categories, however, are not mutually exclusive. To prevent illegal modification/access to internal data by an outsider attacker.įirewall is categorized into three basic types − To prevent an attacker from launching denial of service attacks on network resource. Internet is a dangerous place with criminals, users from competing companies, disgruntled ex-employees, spies from unfriendly countries, vandals, etc. Internal network and hosts are unlikely to be properly secured. It is analogous to locking an apartment at the entrance and not necessarily at each door.įirewall is considered as an essential element to achieve network security for the following reasons − It can be a hardware, software, or combined system that prevents unauthorized access to or from internal network.Īll data packets entering or leaving the internal network pass through the firewall, which examines each packet and blocks those that do not meet the specified security criteria.ĭeploying firewall at network boundary is like aggregating the security at a single point.
Types of Firewallįirewall is a network device that isolates organization’s internal network from larger outside network/Internet. Sometimes the inside network (intranet) is referred to as the “trusted” side and the external Internet as the “un-trusted” side. Network partitioning at the boundary between the outside Internet and the internal network is essential for network security.
Almost every medium and large-scale organization has a presence on the Internet and has an organizational network connected to it.
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