All IPs on the SBL belong to known spammers, spam gangs, or spam support services. The SBL includes IPs from both the ROKSO database and IPs of spam services listed in the Spamhaus database. http://www.spamhaus.org/sbl/
The Spamhaus Project's Register Of Known Spam Operations (ROKSO) Database. ROKSO collates evidence on known hard-line spam outfits that have been thrown off Internet Service Providers over three times. http://www.spamhaus.org/rokso/
The home for domains who don't play by the rules. A number of lists (at present "dsn", "abuse", "postmaster", "whois" and "ipwhois") which contain domains or IP networks whose administrators choose not to http://www.rfc-ignorant.org/
This list contains email servers which are non-secure and potentially servers with dumb and/or malicious users. It is purely composed of data DSBL receives; DSBL should never send out data by itself. http://www.dsbl.org/
Publishes a list of known abusive hosts (open relays, open proxies, spam sources, DoS drones, and more) in various forms including a DNSbl. http://www.ahbl.org