victim server. The provider needs central connectivity to the Internet to manage this kind of service unless they happen to be located within the same facility as the cleaning center or scrubbing center. DDoS attacks can overwhelm any type of hardware firewall, and passing malicious traffic through large and mature networks becomes more and more effective and economically sustainable against DDoS. Application front end hardware Application front-end hardware is intelligent hardware placed on the network before traffic reaches the servers. It can be used on networks in conjunction with routers and switches. Application front-end hardware analyzes data packets as they enter the system, and then identifies them as a priority, regular, or dangerous. There are more than 25 bandwidth management vendors. Application level Key Completion Indicators Approaches to DDoS attacks against cloud-based applications may be based on an application layer analysis, indicating whether incoming bulk traffic is legitimate and thus triggering elasticity decisions without the economical implications of a DDoS attack. These approaches mainly rely on an identified path of value inside the application and monitor the progress of requests on this path, through markers called Key Completion Indicators. In essence, these techniques are statistical methods of assessing the behavior of incoming requests to detect if something unusual or abnormal is going on. An analogy is to a brick-and-mortar department store where customers spend, on average, a known percentage of their time on different activities such as picking up items and examining them, putting them back, filling a basket, waiting to pay, paying, and leaving. These high-level activities correspond to the Key Completion Indicators in service or site, and once normal behavior is determined, abnormal behavior can be identified. If a mob of customers arrived in the store and spent all their time picking up items and putting them back, but never made any purchases, this could be flagged as unusual behavior. The department store can attempt to adjust to periods of high activity by bringing in a reserve of employees at short notice. But if it did this routinely, were a mob to start showing up but never buying anything, this could ruin the store with the extra employee costs. Soon the store would identify the mob activity and scale back the number of employees, recognizing that the mob provides no profit and should not be served. While this may make it more difficult for legitimate customers to get