(CNN)Picture this.
You're sitting at home, enjoying a quiet afternoon, when you hear a knock at your door. Strange. You're not expecting anyone, but maybe it's a neighbor or that package you've been waiting for from Amazon.
But when you open the door, a troop of SWAT officers outfitted in specialized gear swarm your home and order you to get on the ground. They go room to room, shouting commands and training their rifles on anyone they come across.
You've just been swatted.
It's a dangerous prank that's found it's way into the public eye in recent years because of some high-profile, celebrity victims such as Ashton Kutcher, Justin Bieber and Kim Kardashian.
But it reached a new level of notoriety when 28-year-old Andrew Finch was inadvertently killed by police in his Kansas home, a victim of a swatting prank in December 2017.
Friday, Tyler Barriss, the man who made the hoax call to police that precipitated the shooting, was sentenced to 20 years in federal prison after pleading guilty.
Here's what you should know about swatting.
Police made to think a crime has occurred
Swatting is not new -- it was on the FBI's radar as early as 2008 -- but its origins are murky.
At the most basic level, swatting is similar to the prank calls you and your friends might have made growing up.
The difference is, swatting is a prank call made to authorities with the express purpose of luring them to a location -- usually a home -- where they are led to believe a horrific crime has been committed or is in progress.
This results in a forceful response from local police or SWAT teams, who have no way to know the call is a hoax.
Perpetrators sometimes use technology to mask their true location
It's often carried out by the internet-savvy, such as members of online message boards, or, in Finch's case, gamers who are competing and interacting with each other in online games such as "Call of Duty."
The perpetrator might be swatting their target as part of what they believe to be a harmless prank, according to the FBI, or as an act of revenge.
Callers sometimes use "spoofing" technology to make it look as though the call is coming from inside the victim's home, or at least nearby.
Finch did not play video games, his family has said. He was an innocent bystander in the swatting, and had no contact with the other individuals involved.
Barriss, who was in California, made the call that led to Finch's death after being contacted by another gamer who asked him to swat a player he'd been arguing with while playing "Call of Duty."
The gamer gave Barriss an address where the target player had once lived, but was then Finch's home.
Barriss called Wichita authorities, pretending to be inside the Wichita home. According to the 911 tape, Barriss told the operator he had just shot his father and was holding his family hostage at gunpoint, adding, "I already poured gasoline all over the house. I might just set it on fire."
Police arrived, and when Finch opened the door, an officer discharged his weapon, killing him.
Swatting cases are hard to prosecute
There aren't any national statistics about how many swatting incidents occur reach year, the FBI says, but as of 2013 an FBI special agent guessed there were hundreds.
There aren't any federal anti-swatting laws. A bill aimed at combating swatting was introduced in Congress last summer, but it has remained in committee review.
Defendants have faced federal charges before, CNN legal analyst Paul Callan said at the time of Finch's death.
Earlier this year, the Department of Justice said three defendants linked to Barriss were arrested and indicted on charges of conspiracy and conveying false information concerning the use of an explosive device.
Callan said the cases are often difficult to prosecute because many of the perpetrators are juveniles who thought of it as a prank or joke, and it's difficult to prove intent to cause harm.
While some pranksters might think of swatting as harmless, the FBI insisted in 2013 that it has "real consequences."
Not only is it potentially life-threatening, as evidenced by Finch's killing, but it's also expensive.
"It can cost thousands of dollars every time a SWAT team is called out," the FBI said.
