DDoS (Distributed Denial of Service) attacks rely on many computers to overwhelm its victims' networks. Some have promoted DDoS as freedom of speech, but I believe the contrary. DDoS attacks infringe on the victims' freedom of speech by limiting their ability state their views on the Internet. Most DDoS attacks masquerade the attacker behind computers that have been illegally made part of a botnet (large group of computers under the control of an attacker). In effect, the attacker is stealing the voice of others who may not agree with the attacker's views.
DDOS isn't a form of speech, because users can't discern an attack from other technical difficulties a system might have. Users require more legitimate forms of communication to receive the message intended.