Police have always monitored the activity of criminals in their districts. Now, they are learning how to track crime on and better patrol social network sites such as Facebook, MySpace, craigslist, and hi5 - the new cyber neighborhoods - where child predators, gangs looking to recruit new members, identity thieves, cyber bullies, and drug dealers might be lurking.

Yesterday, about 40 officers from law enforcement agencies in the region gathered in King of Prussia to learn how to collect evidence, track suspects, address cyber bullying, and find solicitations for prostitution, alcohol, or drugs.

Capt. Corey MacDonald, a member of the Portsmouth, N.H., police department and a lawyer, guided the officers through the Internet sites as they discovered how to set up their own pages, find friends, and join groups.

The event was sponsored by the Pennsylvania Liquor Control Board with a grant from the National Beverage Control Association.

"This is just another tool officers can use to combat underage drinking in the community," said Leslie R. Coombe, director of the LCB's Bureau of Alcohol Education.

Steve Krolikowski, a public safety officer with Gwynedd-Mercy College, has used social networking sites to investigate vandalism and underage drinking and monitor activity on campus.

"A lot of times, [students] will brag about it and post pictures," Krolikowski said.

MacDonald said that using the sites wasn't just about "catching bad guys." The sites also can be used to identify kids at risk, he said.

When he was working as a school resource officer, MacDonald said, he received a message from a 15-year-old student whose social network site was dedicated to sadomasochistic behavior and demonology.

"I think he desperately wanted someone to notice he was circling the drain," MacDonald said. He alerted guidance counselors, who were able to intervene.

Much of the lecture focused on how officers can teach parents the "best practices" of using the social networking and other commercial Internet sites.

"At the end of the day, this is basic stranger safety taken to the cyber age," MacDonald said.

He advised that parents be counseled to keep computers and cell phones in common areas and to monitor Internet usage history to see which sites have been visited.

MacDonald said it was not up to parents to try to solve cyber bullying. Police can easily have a site removed within a day, deal with the school on any issues, and, if needed, bring criminal charges.

While the easy answer to using social networking sites might be "no," MacDonald said, it is better to have parents or other family members involved in what has become a massive part of their teens' everyday lives.

"Otherwise, they have to learn this whole social network thing all on their own," he said.