“It’s one of those things where this is fun for them just like video games are fun for us,” said Hector Rodriguez, owner of a professional Call of Duty team, OpTic Gaming, whose players have been swatted multiple times while live-streaming at their team home outside Chicago. “It’s a hobby. That’s what makes them smile.”

Game companies like Twitch have publicly said that swatting is dangerous, but that there is little else they can do to prevent the pranks.

Tallying all the swatting calls is difficult. The Federal Bureau of Investigation, for example, said it had no statistics on swatting. Yet reports of such calls have been coursing through gaming news sites with increasing regularity, and there have been more than a dozen prominent examples in the last year.

Richard Beary, president of the International Association of Chiefs of Police, said police departments around the country say swatting is on the rise. In addition to the potential for physical harm, he said, the calls divert resources from local governments.

“It’s an incredible waste of money,” said Mr. Beary, who is also the police chief at the University of Central Florida in Orlando. “It’s dangerous for victims and law enforcement.”

Swatting has become enough of a drain on local resources that the state’s attorney for Will County in Illinois, James W. Glasgow, recently proposed state legislation that would require defendants found guilty of swatting to pay back municipalities for calling on emergency responders. Swatting victims say they have been able to prevent repeated raids at their homes by asking the police to note in records available to emergency dispatchers that they are likely targets.

Tracking the culprits behind the pranks is difficult. While bomb scares and other hoaxes have been around for decades, making threats anonymously has never been so easy.