In the age of the internet booking a vacation is easier than ever. And it is also, unfortunately, easier than ever for con artists to rip you off. Tonight you will see an especially diabolical scam... See More
In the age of the internet booking a vacation is easier than ever. And it is also, unfortunately, easier than ever for con artists to rip you off. Tonight you will see an especially diabolical scam ruining people's dream vacations something you need to be on the lookout for and here is ABC's Rebecca Jarvis. ? Reporter: I bet right about now you are dreaming of a beach vacation? Or maybe a family trip to a big city. This summer, lots of people will be ditching the fancy hotels for apartments, booking them through web sites like air B & B, and brbo, watch out for vacation predators. Those online offers aren't always what they seem. That's what happened at this house in lake tahoe, for our vacation predator case number one. Fake ads online. I should have thought, wow, you know, $400 a night this house is amazing. How could that be? I thought, maybe we were lucky. Cherry Mccaffrey booked this house in south lake tahoe last summerfor the extended family, all 14, on homeaway.com. Her cousin Joyce along with her husband and daughter got there first. While Sherri was still on the road they walked right in. It was totally unlocked. Sprawling, big place. The square feet. Fully decked out. I felt like singing. I was so happy. There was just one problem. So I came home recently and much to my surprise there was a car here in my driveway. Reporter: Sean the owner had not put his home up for rent. I could see there were people milling around in my house I've took a peek through the slats of this house right here and recognized there were total strangers mine house. I entered my house with some trepidation. All of a sudden we saw a man come in. The little girl sort of screamed. I was kind of surprised. I dent know widn't know who it was. Informed them I was the owner. Ser you guys have been scammed. Over the last two weeks I have confirmed episodes with various groups, families, believing that they were renting my properties when indeed they had been scammed. Homeaway.com claims less than one in 10,000 listings are fake. But confirms there were ten other travelers who thought they had rented Sean's house through fraudulent listings seen on their web sites. Authorities are still looking for the cybercriminal who did it. Chris Elliott, author and traveler advocate says he has seen countless cases just like these. And how much money are we talking about here? Most of the people who contact me have lost a couple thousand dollars. Some more than $10 T as far as scams go this is an epidemic. Reporter: Ask John and Nancy don donor. In the past couple years we've been to. China, Japan. South Korea. Vietnam, Thailand. Sing pour. Bali. Reporter: They consider themselves pretty savvy on line. They know the real deal these days booking apartments over hotels. Renting apartments in large cities works out well for us. Reporter: They fell prey to vacation predator case two. Con artists who go fishing for your personal information online. John and Nancy turned to vacation rental site brbo, and after clicking on several properties a great deal landed in their inbox. Free laundry service, airport transfers, even a 20% discount. Just one catch. John had to wire the money to the U.K. I did investigate a little bit. Looked on the web. I didn't find anything. He accepted the deal. Even got a thank you. -Mail with the rental agreement. But then. The website disappeared from the interinternet. Supposed to be as soon as we get the money we will send you further details about the rental. That didn't show up. And then I began to say, well, gee what is going on here? They had been scammed. And here's how it works. A scammer is waiting to intercept e-mail addresses and contacts people directly. In many cases offering properties for rent without the real owners ever even knowing. So we got on the case for John and Nancy. Turns out the manager of the hot New York getaway said he was in London. So we fried tried to track him down. I'm so, we are filming for ABC news. Reporter: Turns out no management company here just an innocent person's house. I was just wondering if you realize this house address has been used online as an address for fraudulent activity? No, no, no. No one living here. This house is -- an apartment. We traced the apartment from the scam artist to a listing inside this New York City apartment building. The owner decloond ined to speak to us on camera, but told us people have shown up not realizing they've been scammed. There are thing you can do to protect yourself. First, never, ever wire money. Use a credit card or paypal instead. Verify who is on the otherened of that rental agreement. Simply by calling. Most legit listings will provide a phone number. Try to use in-house systems that are M more secure. Don't answer anything out of unusual channels. Reverse Google search. Take the image of the vacation rental and run it through Google images if it comes up on multiple sites, renter beware. You have to remember that hundreds of thousand of people use these sites every day. Without any kind of an incident. But use them in an intelligent way. One bedroom, one bath. In hip east village. Hip. Okay. As for the donors it hasn't stopped them from booking their next dream vacation on line. We rented an apartment for the time that we wanted to go. In the future, my basic smell test is going to be much more stringent that in is now. Paranoid. But it was good enough to get by us this time. Reporter: For "Nightline," I'm Rebecca Jarvis, ABC news, New York.
This transcript has been automatically generated and may not be 100% accurate.