The Agile manifesto defines a number of principles, some of which present difficulties for the integration of security engineering approaches, such as frequent delivery of software. There are often numerous security requirements that a product must satisfy, and it is difficult to address these requirements in a short development cycle.
Also, a focus on security decreases the velocity that can be applied to functional user stories in Agile development.
When considering how to handle security requirements, it becomes clear that the same thought and attention must be given to these and to other Non-Functional Requirements (NFRs) such as reliability, performance, scalability, usability, portability, and availability. ...
