The amount is typically under $5,000, with instructions to deposit it and immediately wire a fee to claim the rest of your contest "winnings." Why that amount? Scammers know federal law requires that deposits under $5,000 be "made available" within five days. Your account may show that deposit, but the bank is fronting the money until it collects those funds from the check issuer, which can take about 10 days. When the check proves a dud, you're on the hook for any money drawn from it. In contrast, for checks of $5,000 or more, your bank can wait longer to credit your account.
Sid Kirchheimer writes about consumer and health issues.