Black Hole Routing

Black hole routing (or black hole filtering) is often used to dynamically block hosts that are attacking your network. These hosts are typically found using a network or host IDS.

For More Information

Recommended: Black Hole Routing Tutorial at NANOG
Useful: Blog on Black Hole Routing from Nick Buraglio
  Blog on Black Hole Routing from David Davis

Note that this should only be done by experienced network engineers, as it is fairly easy to break your network if done incorrectly.