A flash crowd event can be characterised by a dramatic increase in requests for a service over a relatively short period of time. Often, these events lead to a loss of service because of the saturation of the target server and associated network resources. This paper presents a set of mechanisms that can be used to make Web servers and associated resources more resilient to flash crowd events. Specifically, we present a novel admission control mechanism that uses a detection mechanism we developed in earlier work to adjust the admission rate of HTTP requests to a Web server. We demonstrate, via simulations, that the admission control mechanism can be used to protect a Web server from the effects of a flash crowd event, protect the traffic of other services that are hosted on the same network as a targeted Web server, and in combination with a push-back mechanism reduce the effect of flash crowd traffic on an ISP's network that is serving the Web server. The mechanisms presented here are exemplars that fit within a resilience strategy we are developing - D²R ²+DR - which is summarised here.