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Firewall
A firewall is a system that blocks access to a network of computers or individual computers by another network (usually the Internet).
A firewall can be a combination of hardware and software or separate solutions (hardware or software).
There are various methods in which a firewall may work:
| 1. | Packet Filtering: Looks at each packet from the network and either rejects or accepts it. This kind of firewall is defined by rules and, while effective, is difficult to configure.
| | 2. | Application Gateway: Applies security mechanisms to specific applications (e.g., FTP, Telnet). This method is effective, but can degrade system performance.
| | 3. | Circuit-Level Gateway: Applies security mechanisms when a TCP connection is established. If the connection is approved, data can flow freely without further checking.
| | 4. | Proxy Server: A proxy server acts as an intermediary and sends all requests and replies to and from the computer accessing the other network. The true network address remains hidden. |
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