The term 'availability' in the context of Secure Software Development Lifecycle (SDL) refers to ensuring that systems, applications, and data are accessible to authorized users when needed. This means that the information must be timely and reliable, without undue delays or interruptions. Availability is a critical aspect of security, as it ensures that the software functions correctly and efficiently, providing users with the information they need to perform their tasks.
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The definition of availability as per the National Institute of Standards and Technology (NIST) Glossary1.
The Microsoft Security Development Lifecycle (SDL) which emphasizes the importance of availability in secure software design2.
General principles of Secure Software Development Life Cycle (SSDLC) that include availability as a key security goal3.