Parents who install a leading brand of software to monitor their kids' online activities might be unwittingly allowing the company to read their children's chat messages -- and sell the marketing data thus gathered, reports the Associated Press (AP).

Software sold under the Sentry and FamilySafe brands can read private chats conducted through Yahoo, MSN, AOL, and other services, and send back data on what kids are saying about such things as movies, music, or video games. The information is then offered to businesses seeking ways to tailor their marketing messages to kids.

"This scares me more than anything I have seen using monitoring technology," said Parry Aftab, a child-safety advocate who is the executive director of WiredSafety.org. "You don't put children's personal information at risk."

The company that sells the software insists it is not putting kids' information at risk, because the program does not record children's names or addresses. But the software knows how old they are, because parents customize its features to be more or less permissive, depending on age.

Five other makers of parental-control software contacted by AP, including McAfee Inc. and Symantec Corp., said they do not sell chat data to advertisers.

One competitor, CyberPatrol LLC, said it would never consider such an arrangement. "That's pretty much confidential information," said Barbara Rose, the company's vice president of marketing. "As a parent, I would have a problem with them targeting youngsters."

The software brands in question are developed by EchoMetrix Inc., a company based in Syosset, N.Y.

In June, EchoMetrix unveiled a separate data-mining service called Pulse that taps into the data gathered by Sentry software to give businesses a glimpse of youth chatter online. While other services read publicly available teen chatter, Pulse also can read private chats. It gathers information from instant messages, blogs, social networking sites, forums, and chat rooms.

EchoMetrix CEO Jeff Greene said the company complies with U.S. privacy laws and does not collect any identifiable information.

"We never know the name of the kid--it's bobby37 on the house computer," Greene said.

What Pulse will reveal is how "bobby37" and other teens feel about upcoming movies, computer games, or clothing trends. Such information can help advertisers craft their marketing messages as buzz builds about a product.

Days before "Harry Potter and the Half-Blood Prince" opened in theaters on July 15, teen chatter about the movie spiked across the internet with largely positive reactions.

"Cool" popped up as one of the most heavily used words in teen chats, blogs, forums, and on Twitter. The upbeat comments gathered by Pulse foreshadowed a strong opening for the Warner Bros. film.

Parents who don't want the company to share their child's information to businesses can check a box to opt out.