Most of the listings on shopping Web sites such as include a photo of the item for sale, but a few instead say “E-mail me for a photo.”

Do not make contact with these online sellers—there’s a good chance that they’re trying to scam you.

If you request a photo of the item, opening that photo might load a virus onto your computer. Or it might open what looks like a Web page on a well-known shopping site—perhaps eBay or—that asks you to enter your user name and password to view the image. Trouble is, this Web page isn’t what it seems. If you enter your password—or your credit card or PayPal account information—it will fall into the hands of the scammer.

Also: Someone selling a high-end item online might try to calm your suspicions by suggesting that you send your payment to an escrow service—a company that holds your money until you receive the item. That might sound like a prudent strategy, but escrow is no guarantee that the seller is legitimate. Scammers sometimes set up phony online escrow services. When you send your money to one of these fake escrow services, you’re really just sending it to the scammer.

If an online seller insists on using an escrow service, walk away from the purchase or insist on selecting the escrow service yourself, then opt for a well-established company such as Type this escrow company’s Web address into your browser yourself—don’t click a link provided to you by the seller. It could misdirect you to a fake site designed to look like the legitimate escrow company you picked.