The pop star told People magazine he decided to get involved when a privacy lawyer told him his name was one of the more frequent ones used by predators looking to lure kids online.
"That was really disturbing," he said.
Lachey teamed up with attorney Parry Aftab to create www.yfly.com, which blocks uninvited guests from intruding on teens using the network.
"We thought we could do something special, if we all put our resources together," Lachey told the magazine. "This is new to me. The whole thing of networking online wasn't around when I was a teen. I wasn't aware of how big a problem this was. And when you are 17 you have no idea of who you are dealing with."
The network is scheduled to launch Thursday.