MAPS (Mail Abuse Prevention System)

Cutely making an acronym out of the spam spelled backwards, MAPS greatest and most controversial contribution to the war on spam is the Real-Time Blackhole List (RBL). The RBL is a list of networks that are either friendly or even neutral to spammers that use those networks to originate or relay spam. Networks are usually added to the list after other avenues, such as complaining to the spammer's ISP or asking a neutral network to stop relaying mail from known spammers, have failed. Neutral networks are included on this list because they are deemed to be failing to do their part. Networks are removed from the list when they have been deemed to comply with MAPS requests or if they are no longer being used by the spammer.

The Mail Abuse Prevention System's Realtime Blackhole List can be used by anybody to configure their own network or mail relay, toward the goal of limiting access to spammers. The MAPS RBL works by creating an intentional loss of connectivity for anyone who chooses to use it. While the idea is to limit that connectivity loss to only networks which are friendly or neutral toward spam, sometimes a spammer hides in and amongst non-spammers so the non-spammers share an unpleasant and negative fate with spammers as well. In other words, the baby will be occasionally thrown out a baby with the bathwater.


The two ways to use the MAPS RBL are: transfer and inquiry. In inquiry mode the administrator starts by knowing the IPv4 address of some host or mail relay, and uses some network protocol to ask MAPS whether that host is listed in the RBL. If the host is so listed, the administrator can choose a next step which is appropriate to the site security policy. This usually means the rejection of all mail from hosts listed in the MAPS RBL, and sometimes, the routing all traffic destined for such hosts to a local black hole . The administrator should never cache the results of a MAPS RBL lookup, since a blackholed host can right itself (by banning the offending spammer from its network) and be removed in a matter of seconds.

In transfer mode, the administrator copies the entire MAPS RBL to one of the hosts on the local network, using a network protocol such as DNS or BGP which allows the site to be updated instantly whenever changes (and most importantly, deletions) occur. Because of the risk of damage to parties who are listed in the MAPS RBL, the MAPS staff actually require administrators to sign and return an indemnification agreement before they will allow the network host(s) to transfer the entire MAPS RBL.

In addition to performing filtering services, every terminated spammer subscription is posted to the RBL so that other ISPs are immediately aware if approached by the spammer of their prospective subscriber's true nature and can refuse to provide service. There are 2,000 ISPs around the world who subscribe to the RBL, representing about 1/3 of the total market, giving the MAPS RBL incredible clout. Faced with the prospects of being cut off from a big chunk of the internet, most ISPs choose to ditch the spammer rather than face user complaints about loss of connectivity.

Detractors of the MAPS RBL claim that the system is imperfect and the "baby" (i.e. innocent networks) are thrown out too often. Other have tried to file lawsuits against MAPS, claiming that they infringe on the right to free speech. MAPS defends itself by stating that, although everyone has the right to free speech, everyone also has the right to not listen to anything they don't want to. Furthermore, they invite other parties to sue them and go as far as posting a page instructing them on how to do so and which companies to ally with in their current lawsuit!