5.1.3 Adaptive and unobtrusive control

Network monitors can be implemented as passive devices. Countermeasures can be applied selectively and against specific sources without having to affect legitimate users^5.1. Rather than having to adopt an all-or-nothing strategy, systems can be built that tighten security gradually as the problems persist.

Footnotes

... users^5.1

The repercussions on legitimate users obviously depends on the countermeasures that have to be taken to protect the assets under attack.