Federal officials said then the near ubiquity of mobile phones made them the most effective means for warning of hurricanes, terrorist threats and missing persons. Emergency alerts are still broadcast via TV, radio and air siren, according to the Federal Emergency Management Agency.
Arriving with distinct ringtones and vibrations, the wireless alerts resemble text messages when they pop up on cellphone screens, but they rely on different technology. All wireless carriers participate in the system, and Hawaii’s emergency agency is among hundreds of federal, state, local, tribal and territorial authorities with the power to use them, according to FEMA.
There are three types of wireless alerts: those issued by the president; those involving imminent threats to safety or life; and Amber Alerts for missing children. More than 30,000 alerts have been sent since the system’s introduction, according to the communications commission. In 2016, law enforcement officials in New York used the system to circulate a kind of digital wanted poster in hunting for a man wanted in bombings in Manhattan and New Jersey. The alerts are free; consumers can use their phone settings to opt out of getting all but those sent by the president.
The system has come under growing scrutiny in recent months, with public safety officials complaining that it requires upgrades on several fronts. Critics say they are often sent too widely, sowing fear among people unlikely to be affected by the threat in question. There have also been calls for the alerts to be sent in languages other than English. The communications commission has approved some changes, but they will not take effect until next year.
Last month, officials from Harris County, Tex., met with commission officials about their frustration over how, during Hurricane Harvey, they could not pinpoint alerts to area residents most likely to be affected by the storm without alarming a broader swath of the county.
The commission, which sets the technical standards for the alerts, is under pressure to update its rules to force wireless carriers and phone makers to work together to ensure that the system is more effective. Last week, Mr. Pai announced a proposal to update the alert system to improve its location-targeting ability.
The inability to target more precisely the areas facing potential threats has deterred some public safety officials from issuing alerts. Senators Kamala Harris and Dianne Feinstein, Democrats of California, wrote to Mr. Pai in October that state residents had not gotten emergency alerts to leave their homes as wildfires raged nearby because of substandard location-targeting and other technical problems.
“These emergency services are caught in a bind between notifying individuals in imminent danger and risking mass panic,” the senators wrote in the letter.
Bruce G. Blair, a nuclear security expert and a research scholar at the Program on Science and Global Security at Princeton University’s Woodrow Wilson School of Public and International Affairs, said he immediately suspected that the alert was false because it involved such a significant national security threat that was directed solely at Hawaii.
If there had been a missile fired toward the U.S., military and intelligence officials would have first notified the president, who would have then decided whether to issue a national emergency alert, he said, although he added that it was reasonable to believe that Hawaii, given its proximity to North Korea, would be on higher alert to such a threat.
Still, Mr. Blair said, the episode did expose a potential flaw in the system that has significant implications.
“This,” he said, “is a system that is hackable and prone to human and technical error.”
Because of an editing error, an earlier version of this article misstated the subject of a meeting attended by Federal Communications Commission officials last month. At the meeting, officials from Harris County, Tex., expressed frustration that they could not pinpoint alerts by location; they were not frustrated that they could do so.