Internet Spyware (I-SPY) Prevention Act of 2004 - Amends the Federal criminal code to prohibit intentionally accessing a protected computer without authorization, or exceeding authorized access, by causing a computer program or code to be copied onto the protected computer, and intentionally using that program or code: (1) in furtherance of another Federal criminal offense; (2) to obtain or transmit personal information (including a Social Security number or other government-issued identification number, a bank or credit card number, or an associated password or access code) with intent to defraud or injure a person or cause damage to a protected computer; or (3) to impair the security protection of that computer. Prohibits any person from bringing a civil action under State law premised upon the defendant's violating this Act. Provides that this Act does not prohibit any lawfully authorized investigative, protective, or intelligence activity of a law enforcement agency or a U.S. intelligence agency. Authorizes appropriations for each of FY 2005 through 2008 to the Attorney General for prosecutions needed to discourage the use of spyware (i.e., software that aids in gathering and sending information about a person or organization, or in asserting control over their computer, without their knowledge or consent) and the practice called phishing (i.e., using the websites of, or e-mails that appear to be sent from, well known legitimate businesses to deceive Internet users into revealing personal information that can be used to defraud those users). Expresses the sense of Congress that the Department of Justice should use this Act and all other available tools to vigorously prosecute those who use spyware to commit crimes and those that conduct phishing scams.