Peer-to-Peer (P2P) payment platforms — such as Zelle, Venmo, Apple Pay, Google Pay, Facebook Payments and Cash App — make it convenient to send someone money from your checking account. Unfortunately, scammers have now discovered them.

Fraud fighters at the National Consumers League and AARP are getting a growing number of complaints from people who have lost money to crooks using P2P apps.

“Because money can be transferred so quickly into someone else’s bank account, these P2P platforms are the perfect payment mechanism for scammers,” said John Breyault at Fraud.org (a project of the National Consumers League). “All you need to get the money is a cellphone number or email address. That’s why it’s so important for people to be really careful when they’re using these apps.”

In a recent news release, Fraud.org said it is seeing P2P payment services used by scammers who place bogus online classified ads for merchandise, or tickets to concerts and sporting events. They’re also becoming an increasingly popular payment method for puppy scams, fake check scams and romance scams. Victims can lose hundreds, sometimes thousands of dollars.

Annette Trujillo, who lives in Arizona, wanted to buy her husband a dog for his birthday. She saw a boxer she liked on a professional-looking website that only accepted payments through Zelle. Trujillo was familiar with P2P payment apps, so she felt comfortable paying the $500 deposit this way.

If you're careful and you know who you're sending money to, these are great tools. If you're not comfortable giving this person a hundred-dollar bill, then don't P2P $100 to him. Paul Benda, senior vice president for risk and cybersecurity policy at the American Bankers Association

“I should have thought about it more, but didn’t at the time,” Trujillo told NBC News BETTER.

Unfortunately, things didn’t turn out as planned. The transaction was never completed, the money is gone and she knows she’ll never get it back. Lesson learned: “If I don’t know you, you’re not getting my money this way.”

Users don't understand the lack of fraud protection

Peer-to-peer apps are not the way to shop online. They are designed to be a quick and easy way to give money to someone you know. For example, you want to pay your part of the restaurant bill at lunch or send money to a friend or family member. The companies offering these apps make this clear in the user agreements.

“Venmo is designed for payments between friends and people who know and trust one another,” Justin Higgs, Venmo’s director of corporate affairs, told NBC News BETTER in an email. “Venmo’s User Agreement states that the platform should not be used to accept payment from (or send payment to) another user for a good or service.”

Early Warning Services, the network operator behind Zelle, said it advises users not to send money to people they do not know or trust. “If a consumer doesn’t know the person, or aren’t sure they will get what they paid for (for example, items bought from an online bidding or sales site), we recommend they do not use Zelle for these types of transactions, which are potentially high risk,” the company said in an email.

Despite this advice, it’s easy to get a false sense of security using these digital payment services.

“People need to understand that a third-party company manages these apps,” said Amy Nofziger, director of the AARP Fraud Watch Network. “Even though your bank may advertise them, it’s not managed by your bank, so it doesn’t have the same consumer protections as using a credit card, debit card or even writing a check.”

Here’s the bottom line: Once the money is sent, it’s gone.

“Under current law, that is considered to be an ‘authorized payment’ and despite your complaint, you do not have a legal right to get your money back,” said Christina Tetreault, senior policy counsel at Consumer Reports.

In preparing its report on P2P payment platforms last year, Consumer Reports asked focus groups what would happen if something went wrong with a P2P payment.

“To a person, the people in our focus groups said the company, the brand that I’m interacting with, would make it right,” Tetreault told NBC News BETTER. “The reality is that the law has not kept up with consumer expectations and the way that money moves today.”

Paul Benda, senior vice president for risk and cybersecurity policy at the American Bankers Association, cautions users to think of P2P transactions as the same as sending cash.

“If you're careful and you know who you're sending money to, these are great tools. If you're not comfortable giving this person a hundred-dollar bill, then don't P2P $100 to him,” Benda advised. “You should not be using these peer-to-peer networks to buy these things without having that product right in front of you.”