Nearly one in three teenagers who use the Internet say they have been harassed online by “cyberbullies” who spread rumors, post embarrassing pictures, make private conversations public and even send threatening messages.

“Bullying has entered the digital age,” the Pew Internet & American Life Project stated this week in a report based on a telephone poll of 935 kids, ages 12 to 17.

Adolescent cruelty has moved from the whispers and shouts of the schoolyard to the online world, where teens often feel insulated from the consequences of their actions, kids reported in focus groups conducted in addition to the poll.

One 15-year-old boy admitted threatening to kill a girl in an electronic message.

“I played a prank on someone but it wasn’t serious,” the boy told researchers. “I told them I was going to come take them from their house and kill them and throw them in the woods. It’s the best prank because it’s like ‘Oh my God, I’m calling the police,’ and I was like ‘I’m just kidding, I was just messing with you.’ She got so scared though.”

Girls reported being bullied online more often than boys, with girls aged 15 to 17 being the most common targets.

Fifteen percent of teenagers who use the Internet said their private e-mail, instant messages or text messages have been forwarded to others or posted to public sites without their permission. Thirteen percent said rumors have been spread about them online, and another 13% have received threatening or aggressive e-mails, IMs or text messages. Six percent said cyberbullies have posted embarrassing pictures of them online.

Overall, 32% of teens online said they have been targeted by at least one of these annoying and potentially menacing forms of bullying. Still, teens reported that bullying was more common in real-world interactions than on the Internet.

In focus groups with Pew researchers, teens said they have to be increasingly careful about what they say because it could be posted on a blog or Web site. One middle school girl said, “I was in a fight with a girl and she printed out our conversation, [changed] some things that I said, and brought it into school, so I looked like a terrible person.”

One girl reported an attack targeted at a gay male.

“I have this one friend, and he’s gay and his account got hacked,” the girl told Pew researchers. “Someone put all these really homophobic stuff on there and posted like a mass bulletin of like some guy with his head smashed open like run over by a car. It was really gruesome and disgusting.”