PORTLAND, Ore. -- Portland-area law enforcement say they are investigating hundreds of cases of child sex abuse, in which the suspect used social media to meet their victim.

And the third local case in a week went before a judge Tuesday.

Sergio Zambrano, 42, of Miami Beach, Fla., came to Oregon for vacation to visit a friend. At least that's what court documents say he told his boss, and police. The web designer admitted to meeting a girl on Instagram two months ago and chatting with her before deciding to fly out.

Sergio Zambrano

Police say he lied about his age to the 12-year-old, and got her to a Motel 6 on Southeast Powell Boulevard, where Portland police say he spent the weekend raping her.

Police say the girl told her parents she was spending the night at a friend's house and when her parents figured out she had lied, Zambrano dropped her off at home.

Zambrano's arrest is the latest in these kinds of nightmare case.

Steven Hilton, 42, of Portland, was arrested last week for Skyping with a West Linn girl, and allegedly trying to get her to meet for sex. He was caught before anything happened.

Steven James Hilton

Related: Portland man tried to lure 14-year-old girl for sex, police say

Ioan Oien, 20, of Salem, was arrested for sexually abusing at least four kids police say he met on Facebook by pretending to be friends of friends of the kids.

Ioan Oien

Facebook, Instagram and Craigslist are common, but Clackamas Detective Erin Schweitzer showed us others you need to watch.

Kik is free. It lets you instantly connect and send photos, messages and videos to anyone in the world. There's no privacy setting, and it's easy to lie.

"Kids are getting themselves into a lot of trouble on this application," Schweitzer said.

Then, there's dozens of apps like Secret Calculator. It looks like a regular calculator icon on a phone, but actually it uses a numeric password to reveal hidden websites, or photos and videos they don't want anyone to see.

"Posting provocative pictures or in their screen name, it might be kind of seductive and so those are red flags for parents, and also green flags for predators," Schweitzer said.

Schweitzer uses computer forensics to track predators online to get arrests. Her team is working about 80 active luring cases right now.

Some tips she uses at home:

  • Set safety settings through your router or internet provider.
  • Only allow "friends" that you personally know join their apps
  • Click on and open all apps.
  • Talk about screen names.

"I think one thing parents often do when they shouldn't is as soon as their child comes to them with a problem, they automatically take that device away and kids are not going to come back to them."

She says your kids will make mistakes online. The most important thing is that they know you want to keep them safe, not just punish them.

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