Comcast Gets Tough on Spam
Found on Slashdot on Saturday, 12 June 2004
The Washington Post is reporting that Comcast, the nation's largest broadband ISP, has started blocking port 25 to reduce Spam. Jeanne Russo said Comcast is not blocking port 25 for all its users because it does not want to remove the option for legitimate customers who process their own e-mail. So the company is monitoring traffic and picking out machines that look suspicious. By blocking port 25, they say they cut Spam by 20% last week." ZDnet has another article, with a nice statistic: Comcast generates 800 million email messages/day, but only about 100 million of those are sent through Comcast's SMTP servers.
Instead of blocking port 25 by default, as many demand, ISPs should monitor connections to SMTP servers and close the port if too many messages are sent in a short time. I don't like the idea of having my access limited because of some spammers. Sometimes it is important to be able to connect to port 25, for example if I have to check if the mailserver still works fine. Administrators could also block all Comcast nets and only allow IPs of their mailservers. Not that hard with Sendmail.