Spam: DNS blocklists are the oldest means of spam-blocking, and are still exceedingly useful; nowadays, many of these are fully automated systems, using proxy-detection algorithms and sensing patterns in mailer behaviour indicative of spam.
(DNS blocklist accuracy figures continued…)
Note, however, that it’s still incomplete:
- some DNSBLs were not measured; these are just the default DNSBL list in SpamAssassin 2.60, excluding RCVD_IN_NJABL_DIALUP (which I had to remove because I can’t parse out accurate data).
- it’s only 1 person’s hand-classified mail.
- SpamAssassin tests more than just the ‘delivering’ SMTP relay; it’ll also look backwards through the headers, at earlier relays, to catch spam sent via mailing lists. This is different from what’s used with most traditional DNSBL-supporting systems.
But the results should still be quite useful.
The time period covered:
- Thu, 21 Aug 2003 17:11:30 -0700 (PDT)
- Sat, 25 Oct 2003 23:11:52 -0700 (PDT)
Recap of the fields:
- SPAM% = percentage of messages hit that were spam
- HAM% = percentage of messages hit that were spam
- S/O = Spam/Overall = Bayesian probability of spam
- RANK = artificial ranking figure, ignore this!
- SCORE = default SpamAssassin 2.60 score
- NAME = name of test. Figuring out the exactly DNSBL should be pretty obvious ;)