The arrest follows a joint 2½-year investigation by the Australian Federal Police, the FBI and the Toronto Police Department, the AFP said in a statement on Friday.
The DDoS attacks took place in 2015 and many of the businesses were contacted by an individual who made unspecified demands from them.
The man was arrested on Wednesday US time. He is now in custody after appearing in the US District Court for the State of Washington in Seattle.
“This is a timely reminder to cyber criminals that international law enforcement is a team sport. Our ability and willingness to work together at a distance and across borders has never been greater,” he said.
“I would like to thank our international partners for their co-operation as well as for their patience and persistence in bringing about this result.
"I would also like to acknowledge the companies who were victims of the attacks for their ongoing co-operation.”