The security of an information system depends on the following factors:

• Confidentiality
  Information must be disclosed only to the right people
• Integrity
  Information must be modified only by the right people
• Availability
  Information must be available to the right people

Collectively, these are known as the CIA-triad.

Sometimes you’ll see accountability as a fourth factor.

There are two different ways of looking at the properties of an information system through the security lens:

1. Security features are features whose sole purpose is enforcing some aspect(s) of security
2. Secure features are all features, security or otherwise, that are designed and implemented in such a way as not to compromise security

The former is usually referred to as information security, while the latter is known as application security or software security.