Internet security is the prevention of unauthorized access and/or damage to computer systems via internet access. Most that gives a user access to a[1]program or system.
Internet security professionals should be fluent in the four major aspects:
Network Address Translation (NAT) typically has the effect of preventing connections from being established inbound into a computer, whilst permitting connections out. For a small home network, software NAT can be used on the computer with the Internet connection, providing similar behaviour to a router and similar levels of security, but for a lower cost and lower complexity.
A firewall blocks all “roads and cars” through authorized ports on your computer, thus restricting unfettered access. A stateful firewall is a more secure form of firewall, and system administrators often combine a proxy firewall with a packet-filtering firewall to create a highly secure system. Most home users use a software firewall. These types of firewalls can create a log file where it records all the connection details (including connection attempts) with the PC.
Some people or companies with malicious intentions write programs like computer viruses, worms, trojan horses and spyware. These programs are all characterised as being unwanted software that install themselves on your computer through deception.
Trojan horses are simply programs that conceal their true purpose or include a hidden functionality that a user would not want.
Worms are characterised by having the ability to replicate themselves and viruses are similar except that they achieve this by adding their code onto third party software. Once a virus or worm has infected a computer, it would typically infect other programs (in the case of viruses) and other computers.
Viruses also slow down system performance and cause strange system behavior and in many cases do serious harm to computers, either as deliberate, malicious damage or as unintentional side effects.
In order to prevent damage by viruses and worms, users typically install antivirus software, which runs in the background on the computer, detecting any suspicious software and preventing it from running.
Some malware that can be classified as trojans with a limited payload are not detected by most antivirus software and may require the use of other software designed to detect other classes of malware, including spyware.
Spyware is software that runs on a computer without the explicit permission of its user. It often gathers private information from a user’s computer and sends this data over the Internet back to the software manufacturer.
Adware is software that runs on a computer without the owner’s consent, much like spyware. However, instead of taking information, it typically runs in the background and displays random or targeted pop-up advertisements. In many cases, this slows the computer down and may also cause software conflicts.
What are keystroke loggers? - detailed advice and information on keystroke loggers, and trojan horses, and how to remove them
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Network cards such as this one can transmit and receive data at high rates over various types of network cables. This card is a ‘Combo’ card which supports three cabling standards.
This article is about computer networking, the discipline of engineering computer networks. For the article on computer networks, see Computer network.
All networks are interconnected to allow communication with a variety of different kinds of media, including twisted-pair copper wire cable, coaxial cable, optical fiber, and various wireless technologies.[3] The devices can be separated by a few meters (e.g. via Bluetooth) or nearly unlimited distances (e.g. via the interconnections of the Internet[4]).
Users and network administrators often have different views of their networks. Often, users share printers and some servers form a workgroup, which usually means they are in the same geographic location and are on the same LAN. A community of interest has less of a connotation of being in a local area, and should be thought of as a set of arbitrarily located users who share a set of servers, and possibly also communicate via peer-to-peer technologies.
Network administrators see networks from both physical and logical perspectives. The physical perspective involves geographic locations, physical cabling, and the network elements (e.g., routers, bridges and application layer gateways that interconnect the physical media. Logical networks, called, in the TCP/IP architecture, subnets , map onto one or more physical media. For example, a common practice in a campus of buildings is to make a set of LAN cables in each building appear to be a common subnet, using virtual LAN (VLAN) technology.
Both users and administrators will be aware, to varying extents, of the trust and scope characteristics of a network. Again using TCP/IP architectural terminology, an intranet is a community of interest under private administration usually by an enterprise, and is only accessible by authorized users (e.g. employees) (RFC 2547). Intranets do not have to be connected to the Internet, but generally have a limited connection. An extranet is an extension of an intranet that allows secure communications to users outside of the intranet (e.g. business partners, customers)RFC 3547.
Informally, the Internet is the set of users, enterprises,and content providers that are interconnected by Internet Service Providers (ISP). From an engineering standpoint, the Internet is the set of subnets, and aggregates of subnets, which share the registered IP address space and exchange information about the reachability of those IP addresses using the Border Gateway Protocol. Typically, the human-readable names of servers are translated to IP addresses, transparently to users, via the directory function of the Domain Name System (DNS).
Before the advent of computer networks that were based upon some type of telecommunications system, communication between calculation machines and early computers was performed by human users by carrying instructions between them. Many of the social behavior seen in today’s Internet was demonstrably present in nineteenth-century telegraph networks, and arguably in even earlier networks using visual signals. [5]
In 1964, researchers at Dartmouth developed the Dartmouth Time Sharing System for distributed users of large computer systems. The same year, at MIT, a research group supported by General Electric and Bell Labs used a computer (DEC’s PDP-8) to route and manage telephone connections.
Computer networks, and the technologies needed to connect and communicate through and between them, continue to drive computer hardware, software, and peripherals industries. This expansion is mirrored by growth in the numbers and types of users of networks from the researcher to the home user.
Today, computer networks are the core of modern communication. For example, all modern aspects of the Public Switched Telephone Network (PSTN) are computer-controlled, and telephony increasingly runs over the Internet Protocol, although not necessarily the public Internet. The scope of communication has increased significantly in the past decade and this boom in communications would not have been possible without the progressively advancing computer network.
Networking is a complex part of computing that makes up most of the IT Industry. Without networks, almost all communication in the world would cease to happen. It is because of networking that telephones, televisions, the internet, etc. work.
One way to categorize computer networks is by their geographic scope, although many real-world networks interconnect Local Area Networks (LAN) via Wide Area Networks (WAN)and wireless networks[WWAN]. These three (broad) types are:
A local area network is a network that spans a relatively small space and provides services to a small number of people. Depending on the number of people that use a Local Area Network, a peer-to-peer or client-server method of networking may be used. A peer-to-peer network is where each client shares their resources with other workstations in the network. Examples of peer-to-peer networks are: Small office networks where resource use is minimal and a home network. A client-server network is where every client is connected to the server and each other. Client-server networks use servers in different capacities. These can be classified into two types: Single-service servers, where the server performs one task such as file server, print server, etc.; while other servers can not only perform in the capacity of file servers and print servers, but they also conduct calculations and use these to provide information to clients (Web/Intranet Server). Computers are linked via Ethernet Cable, can be joined either directly (one computer to another), or via a network hub that allows multiple connections.
Historically, LANs have featured much higher speeds than WANs. This is not necessarily the case when the WAN technology appears as Metro Ethernet, implemented over optical transmission systems.
A wide area network is a network where a wide variety of resources are deployed across a large domestic area or internationally. An example of this is a multinational business that uses a WAN to interconnect their offices in different countries. The largest and best example of a WAN is the Internet, which is a network comprised of many smaller networks. The Internet is considered the largest network in the world.[6]. The PSTN (Public Switched Telephone Network) also is an extremely large network that is converging to use Internet technologies, although not necessarily through the public Internet.
A Wide Area Network involves communication through the use of a wide range of different technologies. These technologies include Point-to-Point WANs such as Point-to-Point Protocol (PPP) and High-Level Data Link Control (HDLC), Frame Relay, ATM (Asynchronous Transfer Mode) and Sonet (Synchronous Optical Network). The difference between the WAN technologies is based on the switching capabilities they perform and the speed at which sending and receiving bits of information (data) occur.
A wireless network is basically the same as a LAN or a WAN but there are no wires between hosts and servers. The data is transferred over sets of radio transceivers. These types of networks are beneficial when it is too costly or inconvenient to run the necessary cables. For more information, see Wireless LAN and Wireless wide area network. The media access protocols for LANs come from the IEEE.
The most common IEEE 802.11 WLANs cover, depending on antennas, ranges from hundreds of meters to low kilometers. For larger areas, either communications satellites of various types, cellular radio, or wireless local loop (IEEE 802.16) all have advantages and disadvantages. Depending on the type of mobility needed, the relevant standards may come from the IETF or the ITU. Networking is meljohn olmikoy anak ni delia ug melchor… pg.ruch…
The network topology defines the way in which computers, printers, and other devices are connected, physically and logically. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions. Commonly used topologies include:
Bus
Star
Tree (hierarchical)
Linear
Ring
Mesh
partially connected
fully connected (sometimes known as fully redundant)
The network topologies mentioned above are only a general representation of the kinds of topologies used in computer network and are considered basic topologies.
