Criminal Spam Act of 2003 - (Sec. 2) Amends the Federal criminal code to prohibit knowingly, in or affecting interstate or foreign commerce: (1) accessing a protected computer without authorization and intentionally initiating the transmission of multiple commercial electronic mail (e-mail) messages (spam) from or through such computer; (2) using a protected computer to relay or retransmit spam with the intent to deceive or mislead recipients or any Internet access service as to the origin of such messages; (3) falsifying header information in and intentionally initiating the transmission of spam; (4) registering for five or more e-mail or online user accounts or two or more domain names using information that falsifies the identity of the actual registrant and intentionally initiating the transmission of spam from any combination of such accounts or domain names; or (5) falsely representing the right to use five or more Internet protocol addresses and intentionally initiating the transmission of spam from such addresses. Prohibits conspiring to do so.
Sets criminal and civil penalties for violations, including forfeiture to the United States of a violator's: (1) real or personal property constituting or traceable to gross profits or other proceeds obtained from such offense; and (2) equipment, software, or other technology used or intended to be used to commit or to facilitate the commission of the offense.
Directs the United States Sentencing Commission to review and amend the sentencing guidelines and policy statements and consider providing sentencing enhancements for violations of this Act for convicted persons who: (1) obtained e-mail addresses through improper means, including by harvesting e-mail addresses of the users of a website, proprietary service, or other online public forum operated by another person, without that person's authorization or by randomly generating e-mail addresses by computer; or (2) knew that the commercial e-mail messages involved in the offense contained or advertised an Internet domain for which the registrant of the domain had provided false registration information.
(Sec. 3) Requires the Departments of Justice and State to report on efforts to achieve international cooperation in investigating and prosecuting spammers who engage in conduct that violates this Act. Calls for such Departments to work through international fora for such cooperation.