input: [Vulnerabilities] application crash due to software error (i.e., a bug) system hangs instead of degrading gracefully under heavy usage distributed denial of service (DDOS) attack power outage diverse types of hardware failure natural disaster riot or terrorist attack inability to restore data promptly after a system failure [Countermeasures] robust application design with comprehensive exception handling provision for ample peak capacity and built-in overload protection limits on request execution times firewall and router configuration with network traffic monitoring and adaptive filtering segmented network topology hardening the TCP/IP stack UPS and redundant hardware, ready to swap into service automated transaction logging and recovery mechanisms [Element / Threat] 
output: Availability maintaining timely access to information and services Threat: Customers are deprived of service - you might as well be out of business.