Simon Cowell ... a hoax distress call was purportedly made from his home. Credit:Getty Images Count Bieber and Cowell as the latest high-profile victims of "swatting", a fast-growing phenomenon masterminded by anonymous mischief-makers who alert police to a bogus crime situation, prompting a tactical response - sometimes by SWAT officers - that involves a high-risk search for phantom assailants. Several officers have already been injured responding to such calls, and officials, including Los Angeles Police Chief Charlie Beck, fear that it's only a matter of time before events turn deadly. Within Hollywood, in an era when breaches of celebrity privacy have never been more invasive - by paparazzi, hacker journalists or even websites that provide detailed information about stars' homes and street addresses - the pranks have taken on troubling dimensions. "Swatting is a very real problem for those in the public eye," said Blair Berk, a criminal lawyer who has represented stars including Mel Gibson, Kanye West and Lindsay Lohan. "It is only a matter of time before someone dies because of this stupidity." What started a decade ago as a malicious prank among computer gamers is quickly evolving into a Grade-A crisis for law enforcement nationwide, encouraging new legislation aimed at stiffer punishments for swatters as well as redoubled attempts to defeat the "spoofing" technology that enables such cyber-troublemaking.

Justin Bieber ... multiple squad cars were scrambled to his house. Credit:Getty Images Chief Beck acknowledged that swatting has stretched the LAPD's emergency response capacity while also endangering victims by placing them in potential confrontation with police firepower. "It not only draws public safety resources away from real emergencies, it places people at significant risk by the dispatch of armed police officers," said Beck. "Our big fear is that [swatting] will become more prevalent." Hoax ... police officers are pictured outside Ashton Kutcher's house in October. Credit:Bob Chamberlin/Los Angeles Times Chief Bill McSweeney of the Los Angeles Sheriff's Department says that the most sophisticated swatting manoeuvres involve tricking caller ID so that an emergency call can be registered as having been placed from inside the very household being swatted.

Investigators say an emergency call reporting an armed home invasion that sent firefighters plus a dozen police officers swarming down on Miley Cyrus's unoccupied Studio City home in August may have originated from a mobile phone, then bounced over several internet providers to hide its origin. Bieber's swatting was called in through a device that allows hearing-impaired callers to send messages over the phone. Hoax ... police officials suspect the same person may have swatted Ashton Kutcher, above, Justin Bieber and Miley Cyrus. Credit:Nic Walker That kind of "spoofing" technology - an elaborate computer fake-out that falsifies data, obscures a person's digital identity and location and can even make a man's voice sound female - is legal and widely available on the web. "Any time you use a telephone or a computer, there is an electronic trail," said Philip Lieberman, founder and president of Lieberman Software, which specialises in computer security. Phone carriers and internet providers monetise every digital communication and have a vested interest in tracking caller origination. "It is virtually impossible not to get caught unless they have a heavy level of sophistication." "Swatting" ... news crews gather outside Ashton Kutcher's home after false reports shot had been fired. Credit:Bob Chamberlin/Los Angeles Times

But even with the advanced software used by the LAPD, tracing spoofed calls or teletexts can be difficult. "If these calls originate with a throwaway phone," McSweeney said, "sometimes those are hard to track." Days after Cyrus was swatted, someone claiming to be a woman locked inside a closet at Ashton Kutcher's Lake Hollywood residence sent a text to emergency services reporting that shots had been fired and individuals identified as "Russian men" were robbing the house. Kutcher was shooting his TV show Two and a Half Men at the time, but dozens of heavily armed officers from several LAPD divisions and a helicopter went to the scene and detained three workmen at the property. The incident came with a steep price tag for the city: $US10,000. Investigators found evidence that the emergency caller may have had Kutcher's house under surveillance, said two people familiar with the investigation who requested anonymity because the investigation is ongoing. They cited the caller's proprietary knowledge of how many people were inside the home before law enforcement arrived. No one has been prosecuted in any of the celebrity swatting cases. But because of similarities in the Bieber, Cyrus and Kutcher incidents, police officials suspect the same person may have swatted the three stars — all of whom, coincidentally or not, have hosted the MTV prank comedy show Punk'd. Kevin Kolbye, assistant special agent in charge of the Dallas-Fort Worth FBI office, began fielding swatting probes in 2007. He views the phenomenon's rapid growth in recent years as a dangerous replacement for a time-honoured practical joke.

"You no longer call pizza [to someone's house] like in the old days," said Kolbye. "Instead, the young generation are getting their kicks putting a lot of people at risk. We've already had a couple of heart attacks and an officer hurt in a collision responding to scene." For years, computer gamers have used swatting to settle petty rivalries that grow out of online one-upmanship playing shoot'em-up titles like Call of Duty: Black Ops. In 2009, Matthew Weigman, a blind 19-year-old hacker from Massachusetts, was sentenced to 11 years in federal prison for his part in a swatting conspiracy with a group of online buddies that staged over 250 swatting incidents in 60 cities. When Los Angeles County Deputy District Attorney Patrick Frey got swatted at his home last July, he thought it might have been in retaliation for posts on his conservative-leaning Patterico's Pontifications blog. In full view of his startled neighbours, Frey was led out in shackles by five armed deputies after a male caller told responders at the Lomita sheriff's station that the deputy district attorney had shot his wife. Outside were four police cruisers, a fire truck, an ambulance, a hazardous materials and a chopper shining a spotlight over his property. Frey's wife was awakened and frisked by police on the front porch while two officers checked on the couple's eight- and 11-year-old children sleeping upstairs. "I'm dealing with psychopaths who know where I live," Frey said. "Someone had it in for me so much, they committed an act they knew could get me killed." No arrests have been made in the case.

In June, another lawyer-blogger, Aaron Walker, was swatted at his home in Prince William County, Virginia. Two officers wielding M4 assault rifles showed up at Walker's town house and ordered him out. The attorney de-escalated the tension, however, by telling the patrolmen: "Let me guess, someone called and claimed I shot my wife." "I believe this to be reckless endangerment if not attempted murder," Walker said. "The intent there was to cause harm. The other angle is, [swatting] degrades the police's ability to trust 911. It used to be they had some degree of trust knowing people had a fear of filing a false police report." In October, Michigan Governor Rick Snyder signed anti-swatting legislation targeting the "people using the internet to report a crime in progress at a different location [altering] the report to look like it's coming from that spot". Under the new law, which takes effect on January 1, perpetrators can receive between five and 15 years in prison (contingent on the number of individuals being hurt or killed by swatting) and fines of up to $US50,000. Currently, the FBI is investigating more than 100 active swatting cases nationwide. Chief McSweeney said the Los Angeles County Sheriff's Department has taken on more than a dozen swatting cases in the last year involving online gamers, celebrities and bloggers. One major stumbling block to police efforts, however, is California law. At present, making a false police report is still only a misdemeanour. But departments across Los Angeles County are beginning to realise that many jurisdictions are wasting valuable resources on swatting call-outs.

"We are going to approach the Legislature with the idea of making swatting a felony," McSweeney said. Senator Ted Lieu oversees a district that includes such celebrity-studded neighbourhoods as Beverly Hills, Bel-Air and Pacific Palisades. He is looking into proposing legislation that would make it easier for district attorneys to make swatting a felony offence. "There may be other ways to do it in which you wouldn't need a law," Lieu said. "But if they can't fix it - if they can't figure out a way to easily trace the people who make these very dangerous 911 calls - I would introduce a bill to try to mitigate the problem. "The issue is, people have figured out how to do this," Lieu said. "And it's only going to get worse unless you can put some consequences in place." Los Angeles Times