Networks

System security

a set of measures taken to protect a computer from harm to its data/software

Cyber attack

an attempt to gain unauthorized access or to control a network

Data loss

An unintentional loss of information that may impact vital data.

• e.g. family photos

Unauthorized data change

entering a computer system to steal data or destroy a network

• can be stolen or leaked

• e.g. product designs, floorplans

data theft

to steal data in order to take advantage of it

• e.g. sales info, virtual money

Computer virus

A piece of malware that infects a computer & replicates itself to pass onto another computer

Penetration testing

Ethical hacking where hackers attempt to break into a network to identify possible security threats

Network forensics

monitoring, recording and analysis of network events

e.g.

• software to analyze unusual activity

• network policies to prevent problems occuring

acceptable use policy

rules that network users must agree to follow to be able to use

disaster recover policy

procedures that the organization will follow to restore normal network operations

anti-malware software

used to detect and remove malware such as viruses

• has a database of virus signatures and looks for its behaviors

firewall

a piece of software or hardware that

monitors traffic in and out of networks

• can allow or block data from entering/leaving

user access levels

a manager controls the level of access people have to networks

encryption

a method of changing the original numbers and characters so they are hidden or disguised.

network

two or more computers connected together so that they can share resources

pros of networks

• improved communications

• improved security

• hardware and software shared

• back-up is possible

LAN(local area network)

a network that is confined to a relatively small geographical area

• general one building or site

• they have their own infrastructure & hardware

LAN charecteristics

• small area

• single site

• cheap to build/run

• cables, wireless, infra-red from organisation

WAN(wide area networks)

connect to larger geographic areas that are at least a mile apart

• many joined together using routers

• external hardware/infrastructure

WAN characteristics

• covers a wide geographical area

• many buildings

• more telecommunication links from external companies

• EXPENSIVE

NIC(network interface controller)

used to convert data from original form to something that can be transmitted via the network

Functions of NICs

• prepares data for sending over the network

• controls flow of data from computer to the transmission medium

• sends data

Transmission mediums

• optional fibers for fiber optics

• air for wireless

• metal for CATS cables

Hubs

simple network devices that allows multiple computers to communicate

Switches

Hubs with more intelligence

• inspect data packets

• only sends data to intended computer, reducing data amounts and increasing speed

Wireless access points

uses a radio transceiver to allow wireless connections to a network

Routers

used to send data signals across the internet

Ring topologies

each device is connected to 2 other devices, forming a ring for signals to travel around.

How ring topologies work

• a small packet called a token is passed around the ring to each computer in turn.

• if there is a request, the ring is modified and goes around the ring until destination is reached.

• it travels in 1 direction only.

pros of ring topologies

• transfers data quickly

• 0 collisions as it all goes in one direction

• easy to increase size

• no hogging on the network

cons of ring topologies

• relies on one cable

• must pass through every computer

• difficult to locate network problems

• anything faulty will cut off the network

ring topology diagram

star topology

switch in the middle with cables running from it to each swtation

How star topologies work

• signal is received by a hub and re-transmitted down every other cable segment

• only the computer that is addressed will act upon it

pros of star topologies

• fast and dedicated connection

• won’t slow down as much

• secure connections

• easier to trace issues

• easy to increase size

cons of star topologies

• expensive cable costs

• no other ways of sending/receiving data

• complex operation

• congestion may occur

• management

star topology diagram

mesh network

no central connection point.

• each device is connected to at least one other node and they all act as relays

node

basic unit of data structure

pros of mesh topology

• received quickly

• no node is isolated

• operation at the same time

• easy to increase size

cons of mesh topology

• impractical set up due to high numbers

  • requires maintenance

mesh topology diagram

full mesh

directly connected to every other node.

partial mesh

not all nodes are connected to one another

• each node is still connected with another

• less routes meaning easier installation and better speed.