Explanation/Reference:
Explanation:
The value of an information system should be based on the cost incurred if the system were to become unavailable. The cost to design or recreate the system is not as relevant since a business impact analysis measures the impact that would occur if an information system were to become unavailable. Similarly, the cost of emergency operations is not as relevant.

Section: INFORMATION SECURITY PROGRAM MANAGEMENT
Explanation/Reference:

Section: INFORMATION SECURITY PROGRAM DEVELOPMENT
Explanation:
Two-factor authentication provides an additional security mechanism over and above that provided by passwords alone. This is frequently used by mobile users needing to establish connectivity to a corporate network. IP address packet filtering would protect against spoofing an internal address but would not provide strong authentication. An intrusion detection system (IDS) can be used to detect an external attack but would not help in authenticating a user attempting to connect. Digital signatures ensure that transmitted information can be attributed to the named sender.