The sweepstakes scam starts with a phone call from someone claiming to be a Federal Marshal or another type of law enforcement agent. They tell the person who answers the phone that they are from the PCH Prize Patrol, and they are going to deliver a prize of $90,000 or more to their home. They just need the so-called winner to wire them some money first to cover "insurance."
This has already struck two of my Top Warning Signs of Sweepstakes Scams: warning sign #1, "Sweepstakes Scams Require You Pay to Receive the Prize" and Warning Sign #10, "Sweepstakes Scams Can Pose As Government Organizations."
If a real law enforcement officer does call your home, you can always ask for a name, department, and badge number, and call to verify that the officer is legitimate, according to Channel 9's article. I'd add that you should be sure to look up the number of the law enforcement agency yourself. It's easy for a scammer to get a friend to pose as a supervisor to verify his story.
Publisher's Clearing House also offers a phone number you can call to verify whether you've really won a prize. You can find it in my Publisher's Clearing House FAQ.
In addition, remember that the Publisher's Clearing House Prize Patrol does not include law enforcement officers. Federal Marshals do not call people with win notifications. And most of all, you never have to wire money to anyone to receive a legitimate prize.