The Wire Fraud statute--Title 18, United States Code (USC), Section 1343--makes it illegal to cause any electrical signal to cross state lines (including the borders of the United States as a whole) in the course of a scheme to defraud. By the very nature of the Internet, it is highly unlikely that any communication would not cross a state line. Wire transfers--either through a bank or through a money transfer agent such as Western Union--will in most circumstances be sufficient to trigger 18 USC 1343 when such transfers are part of a scheme to defraud.

The Mail Fraud statute--18 USC 1341--makes it illegal to cause anything to be sent through the U.S. mails in furtherance of a scheme to defraud. For the purposes of this statute, items sent via commercial carriers such as FedEx, United Parcel Service (UPS), DHL, and others also implicate the Mail Fraud statute.

Implicit in both statutes is the making of a false statement. It is not necessary that the person executing the scheme be the one who initiates the mailing or use of interstate wires--causing others to take such action is sufficient to violate the statute. There is no dollar-value minimum in either of these statutes. Both are felony-level crimes, punishable by up to five years imprisonment, plus fines of up to $250,000.

Other federal statutes that are violated in common Internet Fraud schemes are:

18 USC 1029, Access Device - Credit card numbers, Social Security Account Numbers, Bank Account numbers, Dates of Birth, and even zip codes or telephone numbers in some situations, can be considered Access Devices.
18 USC 2314, Interstate Transportation of Stolen Property - Transporting forged or counterfeit securities (e.g., cashier's checks) across state lines is a violation of federal law which is punishable by up to 10 years imprisonment, plus fines of up to $250,000.
18 USC 1344, Bank Fraud - Making false statements in the execution of a scheme to defraud a Federally-insured financial institution is punishable by up to 30 years imprisonment and fines up to $1,000,000.
In addition the these, other federal statutes may apply depending on the circumstances of a particular crime. Also, the individual states have laws which either address Internet Fraud specifically or incorporate it under more general theories. Laws concerning Theft by Deception, for example, do not generally distinguish between the means to execute the Theft and so apply as readily to the Internet as to more traditional confidence schemes.

In the state of Florida, there are very strong laws concerning Identity Theft. Those laws are often violated in Internet Fraud schemes which involve credit cards. The penalties under Florida's laws can in certain situations be much more severe than those available under federal law.

Common Internet Fraud schemes are explained here.