When we talk about confidentiality of information, we are talking about protecting the information from disclosure to unauthorized parties.
Information has value, especially in today’s world. Bank account statements, personal information, credit card numbers, trade secrets, government documents. Every one has information they wish to keep a secret. Protecting such information is a very major part of information security.
A very key component of protecting information confidentiality would be encryption. Encryption ensures that only the right people (people who knows the key) can read the information. Encryption is VERY widespread in today’s environment and can be found in almost every major protocol in use. A very prominent example will be SSL/TLS, a security protocol for communications over the internet that has been used in conjunction with a large number of internet protocols to ensure security.
Other ways to ensure information confidentiality include enforcing file permissions and access control list to restrict access to sensitive information.