SPEWS Collateral Damage
SPEWS is a popular anti-spam black hole list. It's run by an anonymous group and few know how sites get listed. One thing that is known, however, is that SPEWS favors listing address blocks of ISPs that host spammers. This collateral damage is supposed to put extra pressure on ISPs to adopt strict anti-spam policies.
An example of how this policy harms innocent entities appears on The Linux Kernel Archives site. To quote:
linux.kernel.org, our mailing list server, keeps getting listed in the SPEWS RBL due to numerical proximity with an alleged spammer. We have pointed this out to them on several occations, and they usually fix it -- but a couple of weeks later we find the same problem. For obvious reasons, we do not recommend that you use the SPEWS RBL or any site that derive from their information, including relays.osirusoft.com; see this page.
Please note that The Kernel Dot Org Organization do not endorse or support spam in any shape, way or form, and certainly do not recognize any sort of "right to spam." Spam is at the very least offensive and virtually always fraudulent, theft of service and invasion of privacy. We appreciate that it's a hard and thankless job to run after spammers, and appreciate the services that well-run RBL services provide.
Also please note that we are a small not-for-profit organization that is completely dependent on sponsorships and heavily limited by practical constraints; "just move to another ISP" is not a realistic option for us.