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Principles of Security—The CIA Model

A simple but widely applicable security model is the confidentiality, integrity, and availability (CIA) triad. These three key principles should guide all secure systems. CIA also provides a measurement tool for security implementations. These principles are applicable across the entire spectrum of security analysis—from access, to a user's Internet history, to the security of encrypted data across the Internet. A breach of any of these three principles can have serious consequences for all parties concerned.

Figure 1-2. The CIA Triad


Confidentiality

Confidentiality prevents unauthorized disclosure of sensitive information. It is the capability to ensure that the necessary level of secrecy is enforced and that information is concealed from unauthorized users. When it comes to security, confidentiality is perhaps the most obvious aspect of the CIA triad, and it is the aspect of security most often attacked. Cryptography and encryption methods are examples of attempts to ensure the confidentiality of data transferred from one computer to another. For example, when performing an online banking transaction, the user wants to protect the privacy of the account details, such as passwords and card numbers. Cryptography provides a secure transmission protecting the sensitive data traversing across the shared medium.

Integrity

Integrity prevents unauthorized modification of data, systems, and information, thereby providing assurance of the accuracy of information and systems. If your data has integrity, you can be sure that it is an accurate and unchanged representation of the original secure information. A common type of a security attack is man-in-the-middle. In this type of attack, an intruder intercepts data in transfer and makes changes to it.

Availability

Availability is the prevention of loss of access to resources and information to ensure that information is available for use when it is needed. It is imperative to make sure that information requested is readily accessible to the authorized users at all times. Denial of service (DoS) is one of several types of security attacks that attempts to deny access to the appropriate user, often for the sake of disruption of service.

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