Spamhaus

Spamhaus is an international nonprofit organization that monitors and reports on email spam and related online abuse. It provides real-time threat intelligence to help network operators, mail servers, and security products block unwanted traffic. The organization operates widely used DNS-based blacklists that feed filtering systems around the world.

Its core offerings include the Spamhaus Block List (SBL), the Exploited Hosts List (XBL), and the Policy Block List (PBL). The SBL identifies sources known to send spam or be involved in abuse, the XBL aggregates IPs associated with malware-infected machines and botnets, and the PBL lists dynamic or residential ranges that should not be used for servers. These lists are integrated into many mail gateways and security appliances to reduce spam, phishing, and malware distribution.

Spamhaus was established in the late 1990s by volunteers and security researchers who sought to coordinate community-driven efforts against unsolicited email. The organization operates on a not-for-profit basis and relies on donations as well as paid services to support its operations and data quality efforts. It collaborates with Internet service providers, hosting companies, security vendors, researchers, and, at times, law enforcement, to investigate abuse and publish up-to-date listings.

In 2013, Spamhaus experienced a high-profile distributed denial-of-service (DDoS) attack, one of the largest recorded at the time, which temporarily disrupted access to its services and underscored the importance of its threat intelligence. Since then, Spamhaus has continued to maintain and expand its blocklists and related guidance for responsible use of DNS-based filtering.