Nigerian 419 Scam
This is the original scam from which all the others have developed. This involves the victim receiving a letter, fax, or e-mail from someone claiming to be a high level government official from a foreign country, commonly Nigeria. Sometimes they claim to be the wife of a high-ranking government official that has died or been killed.
The individual tells the victim that they have a large sum of money, often from a US contract with their country that they and their associates would like to invest in the United States. They seek the assistance of someone with a US bank account to assist them to get the money into the country in exchange for a percentage of the money.
If the victim agrees to help, they will be asked to wire money to pay expenses or to bribe officials to release the money. If the victim does not have the money, they will often be sent a check that they are instructed to cash or deposit and then wire the money (usually via Western Union or Money Gram). Of course the check is counterfeit, and comes back after the money has been wired.
This scam can escalate to huge sums of money if the victim wires the "bribe money" from their own funds. This signals that the customer has money and can likely deposit a larger check without raising suspicion.