(NewsNation Now) — Venmo users seeing money from a stranger sitting in their account might want to be wary of those free funds— it could be a scam.

The way the scam works is that Venmo users will get an alert on the app from someone they don’t know, saying they just sent the user hundreds of dollars. Then, the user gets a message saying it was sent by mistake, and the person needs the money sent back.

Steve McFarland, CEO of the Better Business Bureau, says this is a common trick, though. The scammer uses a stolen credit card to send the money. Since it’s fraud, that money will never clear, but the scammer messages Venmo users quickly before they realize that. So then, the money sent back to the scammer is straight from the Venmo user’s own bank account.

Because Venmo offers no fraud protection, there’s no way to get that money back.

“At the BBB we get over 1,000 complaints per day,” McFarland said. “There are scammers galore now on the internet and we’ve seen an exponential increase in scams.”

So what can you do to protect yourself?

For one thing — do not send the money back. If it’s fraudulent, the money should disappear on its own. You should also adjust your settings to “private” on Venmo.