A letter scam in Nigeria is a scheme in which a sender offers someone a commission - usually via email - for helping them transfer a large amount of money.
Nigerian scammers are hoping that the offered fee will be attractive enough to get recipients to send thousands of dollars to a stranger.
The reasons given for a transfer can vary from a government freezing an account to an inheritance without a beneficiary.
Letter scam in Nigeria is also known as prepaid scam or 419 number scam.
The name refers to the prevalence of these scams in Nigeria in the 1990s.