The settlements marked the latest development in a U.S. crackdown on Internet gambling, which has attracted a large number of Americans using offshore gaming Web sites.

The Microsoft settlement totals $21 million, including $4.5 million to the United States and a $7.5 million contribution to the International Center for Missing and Exploited Children, the Justice Department said in a statement Wednesday.

Microsoft also agreed to provide a $9 million campaign aimed at showing young Web users that online gambling is illegal under U.S. law. Microsoft did not admit wrongdoing in settling the allegations that the software and Internet giant received payments from online gambling businesses for advertising.

Google agreed to pay $3 million to settle similar charges and Yahoo $7.5 million and to fund an online public service campaign discouraging online gambling.

Neither company admitted the allegations.

The three companies could have been prosecuted under the Federal Wire Wager Act, federal wagering excise tax laws, and various state statutes and municipal laws prohibiting gambling.

"These sums add to the over $40 million in forfeitures and back taxes this office has already recovered in recent years from operators of these remote-control illegal gambling enterprises," said U.S. Attorney Catherine Hanaway.

"Honest taxpayers and gambling industry personnel who do follow the law suffer from those who promote illegal online behavior."