North Korea has been stepping up its military deterrence against Washington and Seoul and has criticized last month's summit agreement between the two on improving military cooperations.
The launch comes as South Korea and the United States prepare to wrap up 11 days of combined military drills.
Missile tracking data which can detect missile launches is already being automatically shared with US allies through early warning systems.
Pyongyang has said it needs a military reconnaissance satellite to boost monitoring of US military activities.
North Korea said the summit between the United States, South Korea and Japan at the Camp David presidential retreat on Friday was aimed at formulating a "nuclear war provocation."
The hackers were believed to be linked to a North Korean group that researchers call Kimsuky, and they carried out their hack via emails to South Korean contractors.
They also agreed to hold trilateral military training exercises annually and to share real-time information on North Korean missile launches by the end of 2023.
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