Firewall
A firewall is software used to maintain the security of a private network. Firewalls block unauthorized access to or from private networks and are often employed to prevent unauthorized Web users or illicit software from gaining access to private networks connected to the Internet. A firewall may be implemented using hardware, software, or a combination of both.
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| (Firewall between Client & Server) |
A firewall is recognized as the first line of defense in securing sensitive information. For better safety, the data can be encrypted.
Firewalls generally use two or more of the following methods:
- Packet Filtering: Firewalls filter packets that attempt to enter or leave a network and either accept or reject them depending on the predefined set of filter rules.
- Application Gateway: The application gateway technique employs security methods applied to certain applications such as Telnet and File Transfer Protocol servers.
- Circuit-Level Gateway: A circuit-level gateway applies these methods when a connection such as Transmission Control Protocol is established and packets start to move.
- Proxy Servers: Proxy servers can mask real network addresses and intercept every message that enters or leaves a network.
- Stateful Inspection or Dynamic Packet Filtering: This method compares not just the header information, but also a packet’s most important inbound and outbound data parts. These are then compared to a trusted information database for characteristic matches. This determines whether the information is authorized to cross the firewall into the network.
