Computer security is a broad term that cover many aspects such as physical security of the machine, control access to files, etc.. One aspect of the security concerns of network security. With the democratization of the Internet, intrusion attempts to develop. To limit the numbers of these attacks, the best is yet to filter from the network input anything that is not supposed to enter. The system allows the implementation of this filter is called a firewall. A firewall can be defined as a protective device (hardware and / or software) constitutes a filter between a computer or a LAN and an insecure network (Internet or another LAN for example). There are two main types of firewalls:
- Firewalls based on network filtering. These elements function in transmitting information layers of the OSI model. The filtering is done based on the information contained in the headers of the frames, packets (source and destination addresses) and segments (source and destination ports ). This type of filtering does not care about the contents of packets.
- The application firewalls or services. This type of filtering to control the processing of information. In this case, the information contained in the packet can be taken into account. Connection requests are directed to a special program called a proxy or proxy service. It is the latter that will establish the connection to the external service requested.
I am hoping that other members will provide some more notes on this.
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