Even if they cannot decrypt what suspects are saying to one another, a change in the volume of traffic may raise alarm, since a large increase may indicate increased preparation for action, while a sudden decrease may indicate the end of planning and the imminence of action. These considerations do not apply when the targets of analysis follow the military practice of maintaining a steady flow of encrypted communications whether they are needed or not.Slowdown in 'chatter' worries officials: Drop in intercepted communication also noticed before 9/11, CNN, August 6, 2008.
