IN the blink of an eye - or, more precisely, the click of a mouse - a family was destroyed.

Last year, 13-year-old Megan Meier made friends online with a boy named Josh Evans. He seemed to like her - a very big deal to Megan. The, one day, Josh turned on her.

"I don't know if I want to be friends with you anymore because I've heard that you are not very nice to your friends." Soon, "Josh" was spreading rumors and people were posting online notices calling her fat, and a slut, the Associated Press reported.

Megan hanged herself in her closet as a result of the attacks. Recent media reports have focused on a particularly hideous aspect of the case: A mother in the neighborhood was posing as the fictional "Josh Evans," apparently exacting revenge because she believed Megan had been mean to her daughter.

Another part of the story has received less attention, but it's chilling for any parent of teenagers: Megan's parents (and, no doubt, the perpetrator) couldn't imagine how deadly the abuse would turn out to be. They did what any good parents would do: told Megan to ignore the attacks. They told her not to sink to her tormentors' level. And just before she killed herself, they told her everything would be fine.

It's easy for good parents to underestimate the damage that cyber-bullying can cause. After all, "stick and stones can break my bones, but words will never hurt me." Most parents faced taunts when they were kids. It wasn't fun, but it was part of growing up.

What's happening online is something very different. It's far more dangerous. And something parents need to understand.

A child's world is small: school, home, friends, family. An electronic whispering campaign that spreads through a school - or even a class or circle of friends - can be overwhelming.

Cyber-bullying is reaching epidemic proportions. Recent surveys reveal that 54 percent of young people have been its targets, and 80 percent have witnessed it online. Most harassment occurs via instant messaging (47 percent of incidents), followed by e-mail (13 percent) and chat rooms (11 percent).

Much of it is virtually invisible to adults. They don't see what their children see online. And children aren't telling them.

Parents can begin to address cyber-bullying by initiating conversations with their children about their online world. They can also take a more active role in their children's online lives.

THE INTERNET shouldn't be a parent-free zone. For example, let your kids know that you expect them to show you their Facebook or MySpace page. Ask to see the chat rooms they visit. You wouldn't let your children visit a stranger's house without checking it out - the same should apply online.

Schools have a role to play, too.

Half of all cyber-bullying incidents occur at school. They need to create safe opportunities for kids to talk about it and consider its impact. They need policies against online harassment of fellow students. Most important, they should take visible steps to foster a culture of respect and empathy.

The Anti-Defamation League offers a variety of programs to help parents and schools deal with cyber-bullying. The stories we hear are often alarming and sometimes heart-breaking. But we do find reasons for optimism.

Children can be cruel, but they also have a great capacity for empathy. When they hear other kids talk about what it feels like to be on the receiving end of these "harmless pranks," they get it.

One of the most gratifying things about working with children is their willingness to grow, change and learn. As adults, it's up to all of us to make sure they learn the right lessons. *

Randi Boyette is the regional education director for the Philadelphia office of the Anti-Defamation League.