The Spamhaus Project (aka Spamhaus Black List) is one of the world's preeminent anti-spam organizations. Spamhaus fights spam by tracking spam activity via its own network of sensors and data sources and then compiling lists of Internet Protocol addresses associated with spam activity. These IP addresses are added to the Spamhaus Blocklist ("SBL"), which is widely used by ISPs around the world. ISPs use the SBL, along with other data, to determine which IP ranges to block from their network.