internet,intranet and extranet

ADVANTAGE AND DISADVANTAGE

internet

intranet

extranet

computer security risk

Definition of computer security risk:

Any event or action that could cause a loss of or damage to computer hardware, software, data, information or processing capability.

WHAT IS COMPUTER RISK

•Other intruders indicate some evidence of their presence either by leaving a message or by deliberately altering or damaging data.

•Any illegal act involving a computer generally is referred to as a computer crime.

•

•Cybercrime refers to online or Internet-based illegal acts.

•Software used by cybercriminals sometimes is called crimeware.

•Perpetrators of cybercrime and other intrusions fall into seven basic categories:

qHacker, refers to someone who accesses a computer or network illegally. Some hackers claim the intent of their security breaches is to improve security.

qCracker also is someone who accesses a computer or network illegally but has the intent of. destroying data, stealing information, or other malicious action

qScript kiddie has the same intent as a cracker but does not have the technical skills and knowledge. Often use prewritten hacking and cracking programs to break into computers.

qCorporate spies have excellent computer and networking skills.

ühired to break into a specific computer and steal its proprietary data and information.

üto help identify security risks in their own organization.

types of computer security risks-link

peer-to-peer and client server

Categories of network architecture

      -Peer-to-Peer network

          •A simple, inexpensive network that typically connects fewer  than 10 computers.

          •Each computer, called a peer, has equal responsibilities and capabilities.

         •Sharing hardware (such as a printer), data or information with other computers on the peer-to-peer network.

        •Each computer stores files on its own storage devices. Thus, each computer on the network contains both the server operating system and application software.

•All computers on the network share any peripheral device(s) attached to any computer

•Peer-to-peer networks are ideal for very small businesses and home users.

•Some operating systems, such as Windows, include a peer to-peer networking utility that allows users to set up a peer-to-peer network.

Implementing a peer-to-peer network typically involves three steps:

•Install network hardware.

•Configure the peers and workgroup members.

•Share resources to the network.

client/server network

•One or more computers act as a server, and the other computers on the network request services from the server.

•Server, sometimes called a host computer, controls access to the hardware, software, and other resources on the network and provides a centralized storage area for programs, data and information.

•The clients are other computers and mobile devices on the network that rely on the server for its resources.

•

For example, a server might store a database of customers. Clients on the network (company employees) access the customer database on the server.

•Client/server architecture works when the client computer sends a resource or process request to the server over the network connection, which is then processed and delivered to the client.

•A server can manage several clients simultaneously, whereas one client can be connected to several servers at a time, each providing a different set of services.

•The Internet is also based on client/server architecture where the Web server serves many simultaneous users with Web page and or website data.

bus,ring and star topology

bus,ring and star topology

Ring topology:

In a ring topology, the nodes are connected in a ring and data travels in one direction using a control signal called a 'token'.

Advantages:

• Not greatly affected by adding further nodes or heavy network traffic as only the node with the 'token' can transmit data so there are no data collisions.
• Relatively cheap to install and expand.

Disadvantages:

• Slower than a star topology under normal load.
• If the cable fails anywhere in the ring then the whole network will fail.
• If any node fails then the token cannot be passed around the ring any longer so the whole network fails..
• The hardest topology to troubleshoot because it can be hard to track down where in the ring the failure has occurred.
• Harder to modify or expand because to add or remove a node you must shut down the network temporarily.
• In order for the nodes to communicate with each other they must all be switched on.

Bus (line) topology:

Nodes are connected to a main (bus) cable. If data is being sent sent between nodes then other nodes cannot transmit.  If too many nodes are connected then the transfer of data slows dramatically as the nodes have to wait longer for the bus to be clear.

Advantages:

• The simplest and cheapest to install and extend.
• Well suited for temporary networks with not many nodes.
• Very flexible as nodes can be attached or detached without disturbing the rest of the network.
• Failure of one node does not affect the rest of the bus network.
• Simpler than a ring topology to troubleshoot if there is a cable failure because sections can be isolated and tested independently.

Disadvantages:

• If the bus cable fails then the whole network will fail.
• Performance of the network slows down rapidly with more nodes or heavy network traffic.
• The bus cable has a limited length and must be terminated properly at both ends to prevent reflected signals.
• Slower than a ring network as data cannot be transmitted while the bus is in use by other nodes.

Star topology:

In this type of network, a central computer (server) usually forms the main node and the subsidiary nodes are connected to it and to each other through a switch or hub.

Advantages:

• The most reliable because the failure of a node or a node cable does not affect other nodes.
• Simple to troubleshoot because only one node is affected by a cable break between the switch and the node.
• Adding further nodes does not greatly affect performance because the data does not pass through unnecessary nodes.
• Easily upgraded from a hub to a switch or with with a higher performance switch.
• Easy to install and to expand with extra nodes.

Disadvantages:

• Uses the most cable which makes it more expensive to install than the other two topologies.
• The extra hardware required such as hubs or switches further increases the cost.
• As the central computer controls the whole system, the whole system will be affected if it breaks down or if the cable link between it and the switch fails.
• If the switch, the link to the server or the server itself fails then the whole network fails.