The Internet opens a vast world to children, enabling them to learn about distant cultures, view live animal births via webcams or practice difficult math problems.

But as with any tool, the Internet can also have a dangerous side, unlocking an unmonitored planet where strangers may appear to be friendly when they are in fact less than sincere.

In a new study funded by the National Institutes of Health and published in the journal Pediatrics, almost one-third of teenage girls reported meeting face to face with someone they had become acquainted with only online.

Investigators worked with 250 young women ages 14 to 17 and monitored their online and offline activity for one year. About half the girls had recorded histories of either neglect or abuse, while the other half had no such background.

Parents were also involved and were asked to summarize their children’s everyday routines, as well as make mention of any Internet monitoring systems they used.

Sixteen months later, researchers asked the teens to report on any meetings with individuals they had met during the preceding year via the Internet. They found that almost one-third of the girls had in-person get-togethers after initial Internet contact.

Researchers also discovered that those girls with a history of neglect or sexual abuse were likely to post images and verbiage online that could be viewed as sexually overt and provocative … setting the stage for a potentially dangerous rendezvous.

From the parents’ end, software-monitoring systems did not seem to reduce stranger contact … however, more involved, hands-on parenting did.

Researchers noted that although most teen Internet interactions are completely benign, if even 1 percent risk the health and welfare of a child, that is 1 percent too many.