The biggest names on the Internet rolled out a media blitz Wednesday highlighting their latest legal push to eradicate annoying mass emails.

The companies -- the America Online unit of media colossus Time Warner ( TWX), Internet access provider EarthLink ( ELNK), software titan Microsoft ( MSFT) and Net media juggernaut Yahoo! ( YHOO) -- said they filed "the first major industry lawsuits under the new federal anti-spam law."

The companies, identifying themselves as "the country's four leading e-mail and Internet service providers," said they filed six lawsuits against "hundreds of defendants, including some of the nation's most notorious large-scale spammers." The joint effort announced Wednesday is one of many efforts in the commercial, legislative and technological arenas aimed at cutting down on unsolicited commercial email, or spam.

Last year, Congress passed the so-called Can-Spam Act of 2003, the law the companies referenced in Wednesday's media briefing. That law, which went into effect Jan. 1, prohibits such spamming practices as providing misleading "return address" information, using a deceptive "subject" line, sending spam once a person has objected to receiving such mail, automatically harvesting email recipients' names from the Internet, and not providing warning labels for emails with sexually explicit material. The measure provides penalties of $250 per offense, or up to $6 million under certain circumstances.

"Today is a red-letter day for big-time spammers, and the letters they should remember from this day forward are 'Can-Spam,'" said AOL Executive Vice President and General Counsel Randall Boe. "Congress gave us the necessary tools to pursue spammers with stiff penalties, and we in the industry didn't waste a moment -- moving with speed and resolve to take advantage of the new law."

AOL, meanwhile, announced its support Tuesday for a Maryland state law that penalizes spammers with fines and jail terms -- part of a multistate effort to enact such legislation.

"The convenience and efficiency of electronic mail are threatened by the extremely rapid growth in the volume of unsolicited commercial electronic mail," Congress noted in the Can-Spam Act.

Legislators estimated last year that spam accounted for over half of all email traffic, up from 7% in 2001.