Spam - 11
Dateline 12/15/97
MAPS Realtime Blackhole List
The Mail Abuse Protection System Realtime Blackhole List (MAPS RBL) is an effort to limit spam. It is a rather drastic and thus effective effort.
The name, descriptive and demanding to be celebrated as it melts on the tongue, describes the concept: a list of IP addresses that are known sources of spam and thus get blackholed, that is traffic coming from these host or going to them simply disappears as if it were swallowed by a black hole.
How does the 'blackholing' work?
I am not sure if I understood in detail how the Multihop eBGP4 works. One way to implement the spam block is the configure your email server to look up every host that demands your service in the Realtime Blackhole List and deny any further service if the host is found to be a source of spam.
Who gets on the list?
Of course every site where spam originates appears on the list. In many cases this does not affect the spammer alone but also all other customers of the Internet Service Provider (ISP) giving service to them. In this case the ISP is asked to pull the plug on the spammer which will save them from appearing on the RBL.
The most common reason for an IP address to get listed in the RBL is when it is used as a relay for sending spam. Spammers abuse other people's email servers that are configured to forward every mail whose final destination is not the server itself. Blocking mail from such servers may seem like a very hard measure and indeed is as the relay falls victim to spam itself and gets punished and possibly a lot of legitimate mail remains undelivered. But: the amount of spam being transfered can be reduced by this means and it puts big pressure on the insecure relay to close their mail server for third-party traffic.
A third reason to get listed is that an ISP appears somewhere in the spam's contact information (the spammers has an email address or Website). This is even more dramatic as the blackholed network does not send spam at all and indeed it is a bit problematic. At a close look, however, this is only consequent. The whole RLB is a brute force response to spam (which is more brutal). If spammers want to sell something on the Web (and that is what they want) they need a legitimate service provider to host their Website or to handle their email (!) that will not get blocked. Of course they do not misuse these accounts to send spam as that would mean a loss of service. To threaten the ISP with being blackholed if they do not disconnect the spammer and require their users not to practice spamming at all is an effective way of fighting spam.
To get off the RLB is quick and easy… if one complies to the rules.
Censorship, Free Speech
The effects of appearing on the RLB are severe and the conflict with free speech is unavoidable. Blackholing is censorship. But it is not material censorship but a formal one. This matters inasmuch as the decision what is still allowed is not subject to a value judgement as soon as a clear definition of spam has been found. The content of the spam messages (and all subsequently blocked messages that are not spam) does not matter.
Whether we accept, hate, allow, want whatever attitude we have towards spam is still a value judgement, though. When we make this judgement we have to take into account that spam is theft, disregards the receiver's privacy and comes into trouble if we apply some (arguable, of course) moral meta-law.
