By Jonathan Krim Washington Post Staff Writer
Saturday, June 12, 2004; Page D12
Comcast Corp., the country's largest provider of high-speed Internet access, has begun blocking a channel frequently exploited by spammers to send out large volumes of e-mail, a move that many technologists say was long overdue and should be matched by other service providers.
On Monday, the company began targeting certain computers on its network of 5.7 million subscribers that appeared to be sending out large volumes of unsolicited e-mail. Spokeswoman Jeanne Russo said that in those cases, it is blocking what is known as port 25, a gateway used by computers to send e-mail to the Internet.
The result, she said, was a 20 percent reduction in spam.
"We're taking a precision approach . . . against the top talkers of the day," Russo said, referring to the computers being blocked.
The move is the latest in a continuing technological arms race between spammers and Internet companies, which have yet to see lawsuits or federal and state laws make a dent in the volume of unwanted e-mail.
For years, anti-spam activists have been pressuring Internet providers to block port 25 for all users, because it allows e-mail to be sent directly to the Internet without passing through computers operated by the service provider.
E-mail from most residential consumers is processed by their Internet providers' computers, which increasingly have been fortified with filters and other technologies to limit spam and viruses. For these users, blocking port 25 has no impact.
But Comcast and several other Internet providers let many home and small businesses use their own computers, known as servers, to process e-mail. Such customers use their online providers' networks but send e-mail directly to the Internet.
Comcast, with its large number of customers, has drawn the particular ire of the anti-spam community for not addressing the problem sooner. At a recent anti-spam forum, one of its engineers acknowledged that the company had huge numbers of spammers abusing its network.
The issue has become more acute as spammers have gotten more sophisticated. Early on, they would sign up for an Internet account and start sending unsolicited e-mail. When the Internet provider discovered them, they would close up shop and start another account under another name.