firewall A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria. here are several types of firewall techniques: Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing. Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation. Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking. Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses. In practice, many firewalls use two or more of these techniques in concert. A firewall is considered a first line of defense in protecting private information. For greater security, data can be encrypted. The seven layers of the OSI model are as follows: Layer 7 is the application layer: It is the user interface to your computer (the programs), for example, word processor, e-mail application, telnet, and so on. Layer 6 is the presentation layer: It acts as the translator between systems, converting application layer information to a common format understandable by different systems. This layer handles encryption and standards such as Motion Picture Experts Group (MPEG) and Tagged Image File Format (TIFF). Layer 5 is the session layer: It manages the connections or service requests between computers. Layer 4 is the transport layer: It prepares data for delivery to the network. Transmission Control Protocol is a function of Layer 4, providing reliable communication and ordering of data. User Datagram Protocol is also a role of Layer 4, but it does not provide reliable delivery of data. Layer 3 is the network layer: It is where IP addressing and routing happen. Data at this layer is considered a "packet." Layer 2 is the data-link layer: It handles the reliable sending of information. Media Access Control is a component of Layer 2. Data at this layer would be referred to as a "frame." Layer 1 is the physical layer: It is composed of the objects that you can see and some that you cannot, such as electrical characteristics. Admin :- #Cyberlove
Posted on: Thu, 12 Sep 2013 06:02:00 +0000
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