Virtual worlds for children and teenagers—We b sites like Neopets, Club Penguin and Habbo—are a big business. On these sites, children create an avatar and, with it, explore an imaginary universe. They can play games, chat and decorate virtual rooms.

By the end of this year, there will be 70 million unique accounts—twi ce as many as last year—in virtual worlds aimed at children under 16, according to K Zero, a consulting firm. Virtual Worlds Management, a media and trade events company, estimates that there are more than 200 youth-oriented virtual worlds "live, planned or in active development."

As the number of these virtual worlds grows, so, too, does the demand for sophisticated monitoring software and people, called moderators, who can act as virtual playground monitors. Tamara Littleton, chief executive of eModeration, a London-based company providing moderation services, says the most common dangers that children and teenagers face online are bullying and young people's own efforts to share personal information that could enable strangers to identify and contact them in the real world. Sexual predators are always a concern, she says, though she described the likelihood of a child being targeted by an adult with malicious intent as "statistically low."

Meanwhile, there is a continuing game of cat-and-mouse between the young people and the technology designed to protect them.

NetModerator, a software tool built by Crisp Thinking, a private company based in Leeds, England, can monitor online chat "for intent as well as content," says Andrew Lintell, the company's chief executive. To build the tool, he says, Crisp Thinking analysed roughly 700 million lines of chat traffic, some from conversations between children and some, like conversations between children and sexual predators, provided by law enforcement groups.

The software is integrated into a virtual world's site. If the technology uncovers syntax, slangs or other patterns in a conversation that match signs of bullying or sexual predation, it sends an alert to a moderator, who can then "drill down" to look not only at the entirety of the specific conversation, but also at every posting from either participant.

"We can capture a full picture of a user's history on the game," Lintell says. NetModerator also includes a filter that is updated regularly to include new words, abbreviations or character combinations that can be read as words, like "sk8".

Lintell says the company works with several virtual worlds for children. One is the FusionFall site from the Cartoon Network. FusionFall is an online game geared to children ages eight to 14, in which children's avatars fight to save the world with the help of Cartoon Network characters. It uses NetModerator to monitor open chat and player-to-player e-mail, according to Turner Broadcasting, which owns the Cartoon Network.

Keibi Technologies of San Francisco has created technology to determine whether user-generated content—vide os, images and text—contain s objectionable material. Jeff Smith, vice-president for sales and marketing, says the technology is used by several sites aimed at children.

The new technologies made it possible for one site to reduce its moderator staff from more than 20 people to just three or four, Smith says.

For moderators, technical advan-ces have changed the nature of the job, says Bea Marshall, project team leader with eModeration. Marshall, who works from her home in Sacramento, says that when she began moderating children's and teenagers' chat sites nine years ago, she had to identify and respond to "every infraction that came across the screen."

With software technology flagging basic infractions and sending automated warnings, she says she can focus her attention on more subtle or hard-to-interpret messages. This doesn't make the job easy. "Imagine a thousand children, 95% of whom have excellent typing skills, all typing at the same time," she says. "Now try to monitor those conversations."