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7.6 Arithmetic with binary fractions

My final point in the preceding section brings home the fact that integer arithmetic is not really suitable when divisions are to be performed. It is also not suitable where some or all of the values involved in the arithmetic are not – or are not necessarily – integers, and this is often the case. In such cases, arithmetic has to be performed on non-integers.

The most common representation for non-integers is the floating-point representation that I mentioned briefly in Box 3. You
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7.4 Multiplying 2's complement integers

Multiplication can be thought of as repeated addition. For instance, in denary arithmetic

7 × 5

can be thought of as

7 + 7 + 7 + 7 + 7

There is therefore no need for a new process for the multiplication of binary integers; multiplication can be transformed into repeated addition.

In multiplication the result is very often much larger than either of the two integers being multiplied, and so a multiple-length representation may be needed to hold the result of a mu
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16.7 A loyalty card scheme

Supermarkets, and other types of retailer, use loyalty cards to encourage customers to use their particular shops. Points are awarded when a customer spends money in the shop. Supermarkets ‘reward’ their customers by converting loyalty card points into vouchers. They may also give them discount vouchers for a range of products.

Supermarkets use their loyalty card schemes to collect data about their customers. Data about each customer is held in a large database where each customer i
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Learning outcomes

This is what you should have achieved when you have completed your study of this unit:

  • Know the meaning of all the terms highlighted in the text.

  • Be aware of the main processes in an ICT system (sending, receiving, storing, retrieving, manipulating, conveying).

  • Be aware of some of the hardware, software and communication components used in ICT systems.

  • Use a system map or a block diagram to identify the components of an ICT system.
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References

Eyewitness Travel Guide (1997) Amsterdam. London, Dorling Kindersley. pp. 120-1.
Götz, V. (1998) Color and Type for the Screen. Berlin, RotoVision (in collaboration with Grey Press).
Hartley, J. (1994) Designing Instructional Text. 3rd edn. London, Kogan Page.
Michaelis, P. R. and Wiggins, R. H. (1982) ‘A human
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Other approaches to information security management

Many of the approaches to planning an ISMS to be found in the literature follow a three-phase, rather than a four-task, approach. For instance, Moses (1994) stipulates seven steps in three phases:

  • initiation: the identification of information assets and their security requirements;

  • analysis: the identification of possible risks to the security requirements of information assets, of the vulnerabilities to those risks, and
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5.1 Introduction

In this section you will study the process demanded by the British Standard on Information Security Management for planning an information security management system (ISMS). We present ISMS development as a process involving four tasks, each of which may be subdivided into stages. This section also examines the managerial and organisational structures that the Standard recommends to support ISMS development and looks in detail at the ISMS documentation task.


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4.3 Scarcity and shareability

Modern business theory now views an organisation's intangible, rather than its tangible, assets as the reservoir of much of its value. Even a not-for-profit organisation requires information to be shared and protected for its mission to be accomplished. With this new perspective has come a re-evaluation of the methods to be used to protect the value of an organisation. Historically, four walls were all that was needed to demarcate the inside of an organisation from the outside; and four sturd
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3.1 Introduction

The design of a successful information security policy and strategy for any organisation requires an assessment of a number of key factors. These factors can be categorised as either imperatives or incentives. Imperatives are pressures that force you to act. Incentives are the rewards and opportunities that arise from acting.

In Subsection 3.2 we examine the main imperatives confronting organisations. These arise either from threats to information assets or from the obliga
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2.3 What is information security management?

Information security management is the process by which the value of each of an organisation's information assets is assessed and, if appropriate, protected on an ongoing basis. The information an organisation holds will be stored, used and transmitted using various media, some of which will be tangible – paper, for example – and some intangible – such as the ideas in employees' minds. Preserving the value of information is mainly a question of protecting the media in which it is
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1 Why is information security important?

This unit introduces you to information security and its management.

A succinct definition of information security might run as follows:

Information security is the collection of technologies, standards, policies and management practices that are applied to information to keep it secure.

But why is it important to secure information? And how should its security be managed? To s
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12.2 Diallers

Diallers are a problem which only affects internet users who have a dial-up connection. A dialler is a type of software mostly used by pornography vendors. Once the dialler software is downloaded and run, you are disconnected from your ISP and connected to another phone number. You are then charged for the use of this number. While diallers do not spy on you, they are malevolent in nature because they can run up huge costs for the victim. They usually connect to a premium-rate phone line, and
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8 How to protect yourself against spam

People and organisations can only send spam if they have a collection of email addresses to send to. They ‘harvest’ these addresses:

  • from legitimate company databases;

  • from web pages;

  • from chat rooms;

  • by guesswork;

  • from people who use an unsubscribe option.

To minimise the spam you receive:

  • Check whether you can set rules
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7.3 ADV:

Some spam mail includes ‘ADV:’ in the title. This indicates that it is part of the system used in the US to allow spam mail but to highlight that it is an advertisement. You can then make an informed choice as to whether to read or delete the message.

ADV: also allows users of email systems that have filtering facilities, such as Outlook, Eudora or Pegasus, to set a rule that will automatically remove the message. The way this works is that some email systems allow you to define a s
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7.2 Should I unsubscribe from mailing lists?

Many spam messages have a line at the bottom offering to unsubscribe you from a mailing list, but you should be very wary of doing this. Quite often the senders of the spam will use the ‘unsubscribe’ option to verify that your email address is live. They may then sell your address to other people for use in spamming. So using the unsubscribe option can increase your spam rather than reduce it. Our advice is never to use the unsubscribe option unless the mail you receive is from a well-kno
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2.2.1 What is the difference between a worm and a virus?

Unlike a virus, a worm does not infect files on a host computer. Instead it adds a file to the computer that is malicious code, and runs it ‘in the background’. A computer has many programs running in this way in order for its system to operate. For instance, when you create a document you can see the text editor, such as Microsoft Word, Notepad or Star Office, but in the background the spell checker or the printer program are working even though you do not see them on the screen.

W
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Learning outcomes

By the end of the unit you should be able to:

  • distinguish between different kinds of malicious software (viruses, worms and trojans) and protect yourself against them;

  • describe a range of security problems (spam, hoaxes, spyware and adware, homepage hijackers, diallers) and how to deal with them;

  • explain the key principles of safety online;

  • explain the key principles of keeping children safe online.


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4.6 Lineage linked data

Earlier you saw how a genealogical database records relationships between people. A lineage linked database allows queries such as ‘Ada Rosewell the daughter of John Rosewell’ and makes possible the creation of family pedigrees and other charts. For example, the pedigree chart below shows how Alcimenes was the son of Jason (the Argonaut) and Medea and the grandson of Aeson and Alcimedes.

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2.4 Using search engines

Search engines can be very good at finding information since they cover such a huge number of web pages. Unfortunately it can be difficult to find the one you want in the huge number of hits that they return. I can illustrate some of the problems, and some of the strategies you can use to overcome them, with an example.

Let's assume a friend of yours, Jill, has heard you talking about ‘Living with the Net’ and is trying to find out more about the course. What problems might Jill fac
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7.4 Understanding RFID tags

An RFID tag consists of a microchip and an antenna and some kind of encapsulation, such as epoxy resin, to bind the two together and protect them. Tags come in a variety of shapes and sizes (Figure 20), and are generally one of two main types: active or passive. You
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