REUTERS - July 12 - Facebook is among the many companies that are embracing a combination of new technologies and human monitoring to thwart sex predators.Two recent incidents are raising new questions about companies' willingness to invest in safety. Last month Skout admitted its use had led to sexual assaults on three teenagers by adults. Also in June, a teen-oriented virtual world called Habbo Hotel temporarily blocked all chatting after UK television reported that two sex predators had found victims on the site. A solid system for defending against online predators requires both oversight by trained employees and intelligent software. The better software typically starts as a filter, blocking the exchange of abusive language and personal contact information. But instead of looking just at one set of messages it will examine whether a user has asked for contact information from dozens of people or tried to develop multiple deeper and potentially sexual relationship, a process known as grooming. Under a 1998 law known as COPPA, for the Children's Online Privacy Protection Act, sites directed at those 12 and under must have verified parental consent before collecting data on children. Some sites go much further: Disney's Club Penguin offers a choice of viewing either filtered chat that avoids blacklisted words or chats that contain only words that the company has pre-approved. One of Facebook's strategies is to limit how those under 18 can interact on the site and to make it harder for adults to find them. Minors don't show up in public searches, only friends of friends can send their Facebook messages, and only friends can chat with them.