The Dangers of DNS Blacklists

DNS blacklists are lists of servers and networks that are known or suspected of being involved with spam. Properly applied they can provide more effective filtering. However, they are not without problems.

The internet is perhaps the closest thing to a working anarchy I've seen. There certainly are laws that attempt to regulate it. However, the amount of illegal material that's advertised in spam is testament to how little effect they have.

If an individual public blacklist gets to effective at blocking spam email, it gets targeted by the spammers for attack. This has happened several times so far, and in at least a few the spammers managed to shut the blacklist down. This is blatantly illegal, but so are many of their other activities.

Senders of junk email now regularly employ armies of exploited computers to do their deeds. This includes both sending spam and attacking their enemies.

When a blacklist gets shutdown it can result in a number of problems. At best, it simply doesn't provide assistance in spam filtering. At worst, the blacklist owner may decide to go out in a bang. In recent case the list owner configured their servers to report all email as coming from likely spammers.

This created problems across the internet, and for SpamButcher in particular. Subsequently, SpamButcher's anti-spam filters have had blacklist support turned off by default. Users may still choose to enable support for the blacklist of their choice manually.

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