Robert Knowlton, an avid eBay user, bought a pair of slippers from a very reputable dealer on eBay. Soon after he got an e-mail that looked like it was from the dealer where he bought the slippers.

They wanted him to login. "The next thing they do is change your password to theirs, your addresses to theirs and then they can sell things on eBay pretending to be you," said George Graves, an eBay education specialist.

"That gives them access to everything in my account - my credit cards, my bank account," Knowlton said.

The scam e-mail provides what looks like a legitimate link to eBay or PayPal. It is often hard to tell the difference between a legitimate and a fake communication. via NBC

The bottomline is: Always check the url when you have to provide any kind of authentication information anywhere.