Ch 19 Networks

8/2/2019 Ch 19 Networks

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Chapter 19 ICT5

A network exists when 2 or more

computers are connected to each

other by cable, telephone lines orwireless communication.


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Recap from ICT2 Chapter Ch20:

Advantages

Share peripherals (cheaper)

Share datafiles (all haveaccess to the latest info)

Electronic communicationbetween computers such ase-mail and EDI

Software held centrally so

only installed once Security and backup

controlled centrally bynetwork manager

Disadvantages

If client/server networkthen if fileserver fails thenall computers will fail

Network open to moreexternal threats if attachedto a WAN eg Internet

Network may be slow if

much network trafficitdepends on speed ofconnection

Viruses spread quickly


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Recap Types of Network:

Client/Server

Backup easy to perform asjust backup fileserver harddisc

Used on large star or bus

network topologies Most data files andsoftware stored on thefileserver only

Users set up centrally withappropriate access rightsand disc space on fileserver

Powerful central computer

needed called a fileserver

Peer to Peer

Backup has to be donefrom each workstation -YUK

Used with small ring

network topologies Software stored on each

workstation

Users can access data files

& peripherals on otherworkstations if haveappropriate access rights

No fileserver, all

workstations are equal


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Recap Network Topologies:

Star

Central fileserver connects to all the other workstationsvia a hub. Each workstation has its own cable to the hub(Large networks use this method)

BusAll workstations are connected via one central cable andall data is transmitted both ways across it (Used for asmall LAN)

RingAll workstations and peripherals are linked together in acircular configuration and all data is transmitted one wayacross it. (Used for a small LAN) see back pages


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Network Security needs to consider:

Staff- Security on a network is only as good as

its weakest linknormally its staff!! Must have acorporate policy on security supported by Senior

Management and appropriate disciplinary

procedures to back it up.Viruses and illegal software spread easily

especially if backing storage drives and USB ports

are active and employees have Internet and e-mailaccess

Unauthorised access to data files from hackers

Hardware failure need backup (see Ch15)


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Preserving Network Security

1. Physical securitylocks on doors and equipment

restricts access to authorised personnel only.2. Security of backing storagelocking mechanisms on

floppy discs and tapes to prevent overwriting data.

3. Restrict peripheral use - only allowed to print to certain

printers, access certain backing storage drives eg CD

drive, local hard disc etc

4. Restrict access to data files and foldersNo access; read

only; read/write access; full access.5. UserIDs and passwordsnecessary for 3 and 4.


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Staff and Passwords

1. Only acceptable words should be used

Dont use anything obvious not a meaningful word.The operating system can monitor thismust be over acertain length, must contain a mixture of upper &lowercase letters & numbers.

KEEP IT SECRET. Change frequentlythe OS can make you change it after

a set period

OS can lock person out after 3 attempts at password

Have password protected screen saver so can leaveworkstation logged on if essential.


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Illegal access through a WAN

1. Use a firewalla system placed between an internal and

external network that monitors all network traffic comingin and out of the internal network. Only authorised trafficis allowed through. It also filters e-mail and Internetrequests from certain sites.

2. Use data encryptioncodes data so it can only berecovered by someone who has the encryption key

3. Use a call back system so your network makes contactwith another computer system instead of their system

contacting your system (Prevents hackers masqueradingas legitimate systems)

4. Maintain up-to-date anti-virus software


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Duties of a Network Manager

1. Installing software centrally or on individual

workstations. Ensure correct licensing

2. Allocating and maintaining user accounts ofuserIDs, access rights and resource usage

3. Make regular backups (See Ch15)

4. Running and updating anti-virus software

5. Auditing the network by tracking the way

employees use it.


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Network Audit Software

1. It is a key software tool for hunting down fraud andcomputer misuse within an organisation. It helps toensure an organisation conforms to its security policy.

2. All logins and attempted logins are recorded so illegalattempts at a particular workstation are recorded. Thisalso applies to access to datafiles

3. Audit software monitors the number of users on a pieceof software at one time and so prevents more users thanthe licence agreement allows.

4. It produces an audit log. This is used find computermisuse by staff and can also be used as networkaccounting software to charge departments for computertime and resources


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An audit log records the following:

1. Who is using the system

2. What workstation they are using3. Data and time of access

4. What programs they are using

5. What files have been opened, modified and deleted

6. How many reads and writes have been excuted. Howmany times the server as been accessed

7. Failed log on attempts

8. Websites accessed and time spent there.9. Summary reports can be produced of the above for a

single user or groups of users such as a department

Read Question:


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Network accounting Software

Is used to monitor network usage by individualdepartments. For each user the networkmanager can:

Allocate a maximum amount of hard disc space

Allocate a maximum amount of printer credits

Restrict login to a time of day and workstationReports:

Summary reports are produced per departmentcharging for printer use, processor time, backing

storage, network traffic.Usage trends that can be used to plan futureservice provision eg bigger fileserver hard discneeded


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Network User Interface

Security enforced centrally, must have

ID&passwordDifferent desktops and software mandatory

for different types of user to stop

customisation and creates a consistentcorporate image. Also any member of the

department can use the workstation.

The user has more available backingstorage drives

Shared printers so need to choose the right

one


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Question Page 207 Q1

(a) Describe two changes that may be evident to anend-user when they change over from using a stand-

alone computer to a networked environment. 4m

(b) A multinational company has recently created anIntranet, connecting all of its computer systems. Allits sites are now connected using high-speed

dedicated links.(i) Describe one facility that could now be made

available to the company which would improveproductivity. (2 marks)

(ii) Describe two possible problems that may ariseas a result of using this computer network (4m)

(iii) Describe two possible measures that thecompany can take to combat problems caused by

the use of this type of network. (4 marks)


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Answer Page 207 Q1

a)login screen(1) user now has one more stage to completebefore they are able to use their system(1): More disk drives onscreen(1) user now has access to drives that are logical rather

than physical(1):Less control over the interface(1) e.g. inabilityto customise (1) etc

B i) Video-conferencing (1) managers will be able to see eachother without the need for travel costs/long arrangement times(1) OR Ability to share hardware resources (1) means that less

hardware needs to be purchased (1) etcii) Risk of unauthorised access (1) meaning potentially

sensitive/confidential information may be accessible (1) Risk ofviruses (1) all workstations need to have up to date anti-virus

software (1) etciii)Provide user login and password (1) to make it more difficultto enter the system if not authorised (1): Set up requiredprocedures (1) so that users know the tasks that need to becarried out to maintain system security/integrity(1):Use up to

date anti-virus software (1) + example (1) Use a firewall (1)e. . to rovide a filter on traffic comin in/ oin out 1 etc


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What students have problems with:

Dont understand the network is a service

function in a business so needs to:

Charge departments for service

Audit for misuse and future provision Have standard user interface

Also dont seem to understand the jargon

Ch 19 Networks

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Transcript of Ch 19 Networks