It's called the "emergency scam" because its victims are typically asked to wire money to assist some friend or family member in trouble.
Sometimes the scam takes the shape of a phone call from someone claiming to be a relative who needs bail money to get out of jail. The calls, needless to say, are bogus.
But more likely, the emergency scam is perpetrated online, usually after someone's e-mail or Facebook account has been hacked. Urgent (and fraudulent) messages are sent to that person's contacts pleading for some fast cash.
I received just such an e-mail the other day. It was from my 67-year-old stepmom, Judy, who had apparently run into trouble while on a trip to London.
The message said she "got mugged on my way to the hotel and my money, credit cards, phone and other valuable things were taken off me at gun point."
All she needed was $1,800 to pay her hotel bill and return home.
The e-mail, of course, was a sham, even though it had been sent from Judy's actual MSN account and included her actual Florida address and phone number.
She told me she hasn't been to London recently and isn't facing any financial distress. But I was lucky enough to be able to reach her and find this out for myself.
Another recipient of the e-mail, West Los Angeles property manager Fred Droesch, wasn't as fortunate.
"Because the e-mail seemed urgent, I dropped everything," he told me.
Droesch, 76, said he tried to reach Judy but couldn't find her at any of her numbers. So he didn't hesitate. He said he went immediately to a Western Union office and wired $1,800 to London.
Droesch finally reached Judy later that day. When he learned he'd been tricked, he immediately called Western Union and canceled his transaction, and got his money back the next day.
How do things like this happen? Tech experts say the proliferation of Web-based e-mail accounts and social-network sites like Facebook offer easy pickings to hackers keen on passing themselves off as someone else.
In Judy's case, the hacker took control of her MSN account and changed the password so Judy wouldn't be able to send any e-mails debunking the scam. Then he sent his pleas for help to the more than 500 people in her online address book.
The Federal Trade Commission says the number of complaints received about the emergency scam is rising. It's a particularly effective ploy, the agency says, because an appeal from a close friend or loved one can cause people to ignore their natural suspicions. If you receive such a call or e-mail, here's what you should do:
First, try to verify the caller's or sender's identity by asking a personal question that a stranger wouldn't be able to answer. Don't act rashly. Try to call the person back on a known number. If you can't reach him or her, try to connect with another family member.
If you still can't confirm the authenticity of the call or e-mail, contact the police. They'll know if there's a scam going around in a particular area.
Most important, don't wire any money until you're certain the call for help is legit.
And if you do get hustled into sending cash, act fast and try to get your money back before the scammer gets his hands on it.