There's a new twist on prank phone calls. It's called "swatting," and it involves calling 911 and faking an emergency that draws a response from law enforcement -- usually a SWAT team.

Needless to say, these calls are dangerous to first responders and to the victims. The callers often tell tales of hostages about to be executed or bombs about to go off. The community is placed in danger as responders rush to the scene, taking them away from real emergencies. And the officers are placed in danger as unsuspecting residents may try to defend themselves.

In 2007, for example, Randal Ellis, 18, of Washington state was charged by California authorities after pretending to be calling from the home of a married California couple, saying he had just shot and murdered someone. A local SWAT team arrived on the scene, and the husband, who had been asleep in his home with his wife and two young children, heard something and went outside to investigate -- after first stopping in the kitchen to pick up a knife. What he found was a group of SWAT assault rifles aimed directly at him. Fortunately, the situation didn't escalate, and no one was injured.

In the 9-1-1 call, Ellis used an Internet-based phone service for people who are hearing impaired. By entering false information about his location, Ellis was able to make it seem to the 9-1-1 operator that he was calling from the victim's residence.

The schemes can be fairly sophisticated. Consider the following cases recently investigated:

• Five swatters in several states targeted people who were using online telephone party chat lines (or their family or friends).
• The swatters found personal details on the victims by accessing telecommunication company information stored on protected computers.
• Then, by manipulating computer and phone equipment, they called 9-1-1 operators around the country. By using "spoofing technology," the swatters even made it look like the calls were actually coming from the victims.
• Between 2002 and 2006, the five swatters called 9-1-1 lines in more than 60 cities nationwide, impacting more than 100 victims, causing a disruption of services for telecommunications providers and emergency responders, and resulting in up to $250,000 in losses.
• "Swats" that the group committed included using bomb threats at sporting events, causing the events to be delayed; claiming that hotel visitors were armed and dangerous, causing an evacuation of the entire hotel; and making threats against public parks and officials.

The swatters were tracked down through the cooperative efforts of local, state and federal agencies and the assistance of telecommunications providers and first responders. In all, the case involved more than 40 state and local jurisdictions in about a dozen states. All five subjects have pled guilty to various charges.

Another example of "swatting" occurred in Alvarado, Texas in 2006. Matthew Weigman, 18, admitted in June that he and other conspirators agreed to swat Victim #1.Weigman made harassing calls to this victim's residence using a spoof card. Other members of the conspiracy made a swatting call to the victim's residence that resulted in a police response to the residence. The conspirator identified himself as Victim #1 and told the dispatcher that he had shot and killed members of his family, was holding hostages, was using hallucinogenic drugs and was armed with an AK47. The conspirator demanded $50,000 and transportation and threatened to kill the remaining hostages if his demands were not met.

Swatting calls place an immense strain on responding departments. When the calls are made, it is likely that a SWAT team, a helicopter or K-9 units will be deployed, costing more than $15,000.