Parents who install a leading brand of software to monitor their kids' online activities may be unwittingly allowing the company to read their children's chat messages — and sell the marketing data gathered.

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.