ROCKLEDGE, Fla. -- The FBI says it has caught an online sex predator who is more menacing than Central Floridians have ever seen before. He goes beyond trolling chat rooms for young girls and actually hacks into their computers and uses their personal information to threaten them.

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The accused hacker got into the computers of four teenage girls, all friends, three from Rockledge. There was one attempt to threaten the hacker back, but it backfired. Investigators said a child should not communicate at all with a suspected hacker.

It all started on MySpace.com, according to federal documents. Records show that was where suspected hacker and child predator Ivory Dickerson, of North Carolina, first saw a 15-year-old girl from Rockledge and then asked her for nude photos.

Investigators said the accused hacker instant messaged her that "he knew where she lived, then provided the address."

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Computer sex crimes investigators said hackers take the fear factor to new levels, especially with children.

"It's scary, because you don't know where the individual lives. You don't know if he lives next door. You don't know how immediate that threat could be," said Steve McElyea, FBI Task Force member.

Records show the suspected hacker threatened to "e-mail her address online" and "hurt her sister" if she didn't send nude photos. So, the Rockledge High School student told investigators she eventually did, but when she wouldn't send more, he posted her first ones on MySpace.com.

Records show the hacker then pretended to be her online and pressured three of her friends to send nude photos by making threats such as, "Are you sure you want to drive to school tomorrow?" and "You don't want to piss me off" and threatening to make her "the most well-known girl at school."

Investigators said a child who comes in contact with a person who claims to be a hacker should take some immediate steps.

"Shut everything down. Unplug the power. Disconnect your cable outlet for your online service and notify local authorities," McElyea said.

Even more frightening, investigators said, they found Carnival Cruise tickets in Dickerson's house and a videotape of him drinking on a previous cruise with 15-year-old girls.

Investigators said they also found hardcore child porn in the suspected hacker's house, including photos of a bound, blindfolded child hanging from the ceiling, evidence that could lead to more charges.

Federal agents are bringing Dickerson back to Central Florida from North Carolina for prosecution.

The FBI Innocent Images Task Force said making sure you keep up with all security updates on your computer and installing firewall software will help keep hackers out, but there's no guarantee.