Computer Fraud and Abuse Act of 1984 - Amends the Federal criminal code to establish a federal offense of using a computer without authorization or using a computer with authorization for unauthorized purposes with the intent to execute a scheme to defraud, if such conduct obtains: (1) anything of value aggregating $5,000 or more, or creates a loss of $5,000 or more, during any year; (2) classified information; or (3) certain financial records.

Prohibits the unauthorized use of a computer when such conduct modifies, destroys, discloses information or prevents the authorized use of a computer operated for or on behalf of the U.S. government.

Makes it an offense to attempt to commit or to be a party to a conspiracy to commit such an offense.

Increases the penalty for subsequent offenses.

Grants authority to the U.S. Secret Service to investigate offenses under this Act.

Requires the Attorney General to report annually to Congress about prosecutions under this Act during the first three years after its enactment.