It was an organization that developed anti-spam solutions, primarily known for maintaining a Real-time Blackhole List (RBL). MAPS identified and blocked IP addresses that were associated with sending spam or engaging in abusive email behavior. It later expanded to include additional blacklists for open relays, proxies, and other categories of email misuse. Founded in 1996, MAPS played a key role in early efforts to combat email spam before becoming a part of Trend Micro in 2005.