Here's one variation on the classified ad scam that at first caught a Spokane, Wash., resident off-guard.

Ginny Foster had advertised her Olde English Bulldogge puppies in several Washington state newspapers. One night she got a call from an operator who told her the caller would be using relay to communicate with her because he was hard of hearing. When the caller typed a message on his computer, the relay operator would read it to Foster.

The conversation was short -- the con man gave her his e-mail address so that she could send him more information about the puppies.

Foster said it was his e-mail response that tipped her off, partly due to the terrible grammar, but also due to the nature of his request. In the e-mail, he told her he would send a certified Visa Traveler's or cashier's check, which she was to cash and then use the extra money to pay a shipping company that would come pick up the animal.  Luckily, she knew not to send any money.

Foster said the relay call played to her sympathy because she thought the caller was hearing impaired. "If you let that clog your judgment, you're screwed," she says.

Roommate rip-off
How it works: The Internet Crime Complaint Center, or IC3, reports that one of the biggest current overpayment scams involves the use of legitimate rental housing and roommate-matching sites, such as Roommates.com. The scammer contacts people who have placed ads on the site looking for roommates and offers them the first month's rent, the deposit or both in the form of a check or money order.

"Either one is conveniently more than the rent or deposit so the victim is asked to cash the said check or money order and send the difference either back to the would-be renter or to a 'moving company' -- usually a second partner in the scam," says Stacey Brown, an Internet fraud analyst with the IC3.

The cover story may vary, but the theme is the same: Scammers simply use fake money to entice you into sending real money. Get fooled by a phony roommate and you could lose some serious rent money. Brown estimates that victims lose $500 to $5,000, on average.

Being clever may cost you
Just because a check clears does not mean it's a legitimate check. While federal law allows you to access the money within one to five days, depending on the type of money order or check, it can take weeks, or even months, for counterfeits to be discovered, says Grant.

Where to report a scam: