The new law, introduced in the Senate by Senators Conrad Burns (R-Mon) and Ron Wyden (D-Ore) will come into force on January 1, 2004.

Under the terms of the bill, senders of unsolicited commercial e-mail are prohibited from using a false return address, or a misleading subject line.

Such e-mails must contain a valid way for those who receive them to 'opt out' of the mailing list, and must also contain the sender's physical address, as well as a clear indication that the message contains advertising material.

In addition, spammers will now be explicitly prevented by law from harvesting addresses from web sites, and from hacking into computers to disguise the actual origin of unsolicited e-mails.

The bill also authorises the Federal Trade Commission (FTC) to establish a 'Do Not Spam' registry, similar to the 'Do Not Call' list recently established for US citizens wishing to prevent telemarketing calls.

The legislation, when it comes into effect, will supersede 35 existing state anti-spam laws.

In a statement, Senator Wyden welcomed the signing into law of the bill by the President, and revealed that:

"Swift and aggressive enforcement will be essential, and Senator Burns and I will continue to push the Federal Trade Commission and others to use the tools this law gives them to fight against spam."