(MONEY Magazine) – Let's say you wanted to rent your house this summer--one week minimum, please. You placed an online ad and got a response from a South African honeymooning couple asking if your home is available for the entire month of May. Enticing: four weeks, pre-Memorial Day, $4,000. So what if the finances sound a little complicated? The groom-to-be explains in the e-mail that he is a sailor at sea and can't get to a bank. But he'll happily send you what he has: a cashier's check for "$10,700, after which you will deduct the cost of your rental and have the excess amount sent to the agent that will be responsible for my transportation." Stop right there. It may look and feel like a cashier's check, but it is counterfeit. Deposit it, write a check to the "agent" for the $6,700, and that money will end up coming straight out of your pocket. A transparent scheme to some, no doubt, but it's also the latest incarnation of the Nigerian scam, which for almost 25 years has bilked more than $5 billion out of the foolish and the greedy around the world (see "The Scam That Will Not Die," July 2002). This particular twist is relatively tame--most of the bogus money orders are around $10,000. Dave Bollinger of CyberRentals.com says enough of his customers report receiving these e-mails that he's sending out warnings. "The requests are usually for the last minute," he explains, "and maybe for a period you couldn't easily rent." If you suspect you've received a Nigerian scam letter, go to secretservice.gov/alert419.shtml for word on what to do about it. --JOAN CAPLIN