What are the three objectives of information security?

Information security is a relative term. It is effective only when it is balanced with business requirements, cost, and risk mitigation. Learn how to determine security requirements that mesh effectively with your business objectives, create policies that work for your organization, and use technology to implement your policies.

In this chapter:

• The Four Objectives of Security: Confidentiality, Integrity, Availability, and Nonrepudiation

• Roles and Responsibilities

• Security Policy

• Security Technology

Most of us understand how locks, barred windows, lit parking lots, and loud barking dogs can be used to make our office buildings more secure. Computer security can, in many ways, be compared with these physical security approaches. But, as with anything else that we translate from the real world to the computer world, we find that we must very firmly define our terminology and our business needs before the computer version can either be understood or made to work. In this chapter, we will define what computer security is and how it is achieved in a successfully secured organization. If you have no experience with computer security, you probably think that your computers already include solutions to these problems. In fact, most business people believe that. They are wrong.

Objectives of Computer Security

If you are new to computer security, you will soon learn that there is a lot more to it than keeping "evil" hackers out of your systems. Computer security has four objectives: confidentiality, integrity, availability, and nonrepudiation (NR). Securing information is equivalent to ensuring that computers keep your secrets, hold valid information, are ready to work when you are, and keep records of your transactions. Figure 1–1 shows the four objectives.

Figure 1–1 The four objectives of information security.

These first three objectives are the "motherhood and apple pie" of Information Technology (IT) departments. Unfortunately, too much apple pie can make you sick (or at least overweight), and too much security can be bad for business. We hope that this book will prepare you to understand how much security is enough for your business and why it is (and should be) up to you. The fourth objective becomes especially important when you transact business using computers for activities such as online sales or securities trading.

The three objectives of confidentiality, integrity, and availability can never be completely separated. The definitions and solutions overlap among the three. That is not a problem. We just need to keep the end goal in mind: computers that do what we want, when we want because we are the business owners of those computers. But they must do nothing for anyone else.

Confidentiality

The first objective of security is confidentiality: keeping information away from people who should not have it. Accomplishing this objective requires that we know what data we are protecting and who should have access to it. It requires that we provide protection mechanisms for the data while it is stored in the computer and while it is being transferred over networks between computers. We will need to know the application programs that we use (or could use) to manipulate the data and control the use of those applications. Luckily, the Chief Security Officer (CSO) and the IT team will handle the mechanics of doing all this—just as soon as we tell them how to figure out who should have access to which data and applications and how far to go in providing confidentiality (see "Relative Security," later in this chapter).

Key Point

Confidentiality mechanisms keep information from being read by unauthorized people.

In the Internet world, confidentiality has taken on an expanded meaning in the form of privacy controls. For some industries, such as health care and finance, privacy is now a regulatory issue. The U.S., European, Canadian, and Australian governments (with others following) have legislated privacy controls to varying degrees. Even U.S. companies in other industries are now governed by privacy legislation of other countries if they have employees or customers in any of those other geographies. We will cover the legal requirements for security in much more detail in a later chapter. In addition, public demand for privacy has forced many companies to formulate clear privacy policies to prevent their customers from going to competitors.

There are numerous technologies available to provide confidentiality for computer applications, systems, and networks. They will be described with their strengths, costs, and weaknesses in later chapters of this book.

Integrity

The second objective of security is integrity: assuring that the information stored in the computer is never contaminated or changed in a way that is not appropriate. Both confidentiality and availability contribute to integrity. Keeping data away from those who should not have it and making sure that those who should have it can get it are fairly basic ways to maintain the integrity of the data.

Key Point

Integrity mechanisms assure that information stored in the computer is never contaminated or changed in a way that is not appropriate.

But many security failures happen despite reasonably strong controls on who has access. Sometimes, the people we trust are not trustworthy. Sometimes, we need to extend levels of trust to people about whom we know little or nothing, such as temporary workers, third-party business partners, or consultants. Integrity constraints have to go beyond the simple "who" definitions and handle the "what" conditions. Once someone has been granted access, what operations can they perform on our computers? This leads to requirements for detailed constraints on different types of access within the computer system and, thus, to much of the complexity of a modern business computer system. If a typical end user can change the behavior of the operating system or network, anyone inside our company can stop business from being processed—intentionally or not.

The need for data integrity connects computer security to a closely related discipline: business continuity planning and data recovery. Data will eventually be damaged by hardware failure, software failure, human errors, or security failures. Recovery processes are a necessary part of any business IT plan and frequently are under the control of a security department.

Availability

The third objective of security is availability: ensuring that data stored in the computer can be accessed by the people who should access it. Availability is a broad subject addressing things such as fault tolerance to protect against denial of service and access control to ensure that data is available to those authorized to access it. Most computers can at least differentiate between two classes of users: system administrators and general end users. The major exceptions to this rule are the desktop operating systems that have become common on personal computers.

If you read, you'll find references in most IT publications describing Microsoft Windows 95/98, in all its versions, as being insecure. One of the reasons for this is that the operating system has no ability to discriminate between system administrators and general end users. Many other desktop operating systems have this same shortcoming. Anyone who uses one of these computers can change its security environment and can, in fact, turn security off. A few users in an enterprise deciding to turn off security can open the network to attack in some cases. Of course, these operating systems also have many other security weaknesses, even when security is turned on.

Key Point

Availability means ensuring that the data can be accessed by all authorized people.

Authorization should extend well beyond discriminating between system administrators and general end users. In a well-secured computer system, each user is assigned a series of corporate roles, typically by the Human Resources department, based on his or her job description. The computers determine exactly what each user is allowed to do, using those roles. This "role-based authorization" allows even system administrators to be limited in their control of the computers. This is frequently used to stop the otherwise powerful administrators from turning off security or auditing and, thus, providing themselves with unreasonable and undetectable power over their employers.

In the Internet world, availability has also taken on an expanded meaning. One of the most common forms of security problem for Internet applications is the "denial of service" (DoS) attack. This is a focused attempt by a cyberattacker to make a computer system and its data unavailable. This can be done in two ways. First, the attacker may try to damage the target computer or some network component on which the computer depends. Second, the attacker may simply send so many messages to the target computer that it cannot possibly process them all. Other people attempting to use that computer for legitimate purposes find that the computer is too busy to service them.

Nonrepudiation

Security is a large enough task just trying to meet the confidentiality-integrityavailability objectives. Technologies used for those objectives are also used to create business-related functions for NR, which allows the formation of binding contracts without any paper being printed for written signatures. NR is new and not broadly used, but most security experts agree that it will be based on digital signatures, which are described in Chapter 13, "Digital Signatures and Electronic Commerce." The use of security-related technologies and the need for a strongly secured and trusted instrument for creating digital signatures have led to NR becoming a new security objective.

Nonrepudiation Benefits

NR has many valuable goals, including assuring that messages came from the person whom the message claims sent it and that the message has not been altered in transit. One of the beneficial side effects to these mechanisms is the ability to prevent users who send messages from denying that they were sent. This has significant value in many business situations.

For example, in a business-to-consumer (B to C) transaction, consumers place orders. Sometimes, they change their minds and decide they don't want what they ordered and will claim that they never ordered merchandise or that the order was not what they requested. NR mechanisms keep consumers honest and protect businesses in these situations.

Another business that benefits significantly from NR is the online auctioning business, where clients of varying integrity and intent exchange merchandise, using the business as a go-between. In this environment, it is mission critical to have mechanisms that keep everyone honest.