The U.S.'s largest broadband service has begun blocking a network loophole they say spammers exploit rather commonly.
Cable giant Comcast said it will block "port 25" – the gateway most computers use to send e-mail – for any accounts they suspect of sending massive volumes of spam. Comcast determines their blocking choices based on subscriber accounts with the most outbound activity, according to published reports.
"We don't think it's the right approach to blanket port 25," Comcast vice president of operations Mitch Bowling told CNET. "The right approach is to seek out people who are spamming our network and others."
BroadbandReports.com is taking credit for first disclosing the Comcast blocks earlier this week. "Comcast, the nation's largest cable provider and self-proclaimed 'biggest spammer on the internet,' may finally begin 'targeted' blocking of some users' outgoing port 25/tcp traffic to help reduce spam, according to discussion in our Comcast forum," said BroadbandReports.com writer Karl Bode. "The tactic, discussed at length in a previous BBR report, has grown in popularity among ISPs; particularly with the increase of infected PCs acting as unwitting spam relays."
Comcast itself is not known to be a spammer. The "self-proclaimed 'biggest spammer on the Internet'" alludes to a previous incidence in which Comcast, noting that Comcast customers sent out an estimated 800 million e-mails a day, most of which were going by way of worm or virus-compromised machines turned into spam conductors, called itself the unwilling largest spammer in cyberspace. But the company also came under some fire over allegations that they hadn't addressed the problem previously.
