A register of known spam operations (ROKSO) is a database of the most harmful spammers. It usually contains 100 to 150 hard-line spamming outfits made up of professional spammers who have been caught by law enforcement or other agencies three or more times for distributing up to 80 percent of most spam. Working in conjunction with law enforcement, ROSKO provides evidence-based spamming data along with aliases used by spammers. This evidence includes spamming methods, IP addresses, history and other pertinent data.

Those listed on the ROKSO have been denied Internet access by three or more Internet service providers as a result of three known spamming operations that have been implemented in far-reaching measures. Most ROKSOs deal with pharmaceutical scams, while other promote Internet pornography and other illicit online services.