The following is a list of tests that we run against the E-mails arriving at the spamtrap, and what percentage of the spam they caught (it may be easier to read if you use a fixed-width font):
WEIGHT10 99.60% WEIGHT20 97.93% SPAMCHK 95.73% SPAMMANAGER 95.09% NOLEGITCONTENT 94.67% SNIFFER 93.59% IPNOTINMX 89.14% SPAMCOP 78.34% DSBLALL 58.57% DSBL 57.77% BADHEADERS 49.65% WIREHUB-DNSBL 46.71% MONKEYPROXIES 44.17% MAILDEFLECTOR 43.34% HELO 38.99% NOPOSTMASTER 38.69% REVDNS 38.20% FREEMAIL 35.10% BLITZEDALL 33.80% BLARSBL 32.59% ROUTING 30.76% NOABUSE 28.57% FIVETENSRC 28.36% EASYNET-DNSBL 26.89% OSPROXY 24.45% OSSRC 23.67% SPAMHAUS 23.36% DORKZTL 19.78% SPAMHEADERS 19.60% OSSOFT 17.77% EASYNET-PROXIES 17.01% IPWHOIS 12.64% DSN 10.04% COMMENTS 9.62% BASE64 8.87% COMPU 8.79% INTERSIL 8.65% VOX 8.14% DNSRBL-SPAM 8.08% DELINK 6.38% FABELSOURCES 6.06% FIVETENIGNORE 5.31% SPAMBAG 4.93% LNGSDUL 4.28% NJABL 3.86% OSRELAY 3.46% DNSRBL-DUN 2.57% BADWHOIS 2.49% KUNDENSERVER 2.35% ORDB 2.33% MAILFROM 2.04% NJABLDUL 1.83% LNGSBLOCK 1.53% OSDUL 1.26% WIREHUB-DYNA 1.20% DORKS 1.16% PIGS 1.09% KITHRUP 1.00% FIVETENOTHER 0.84% EASYNET-DYNA 0.74% DSBLMULTI 0.68% NONENGLISH 0.45% JIPPG-DUL 0.33% FIVETENOPTIN 0.31% FIVETENMULTI 0.20% DORKRELAYS 0.19% ABL 0.15% DEVNULL 0.08% FLOWGO 0.05% DNSMAILLIST 0.04% JIPPG-DULJP 0.01% FIVETENWEBFORM 0.01% OSLIST 0.01% LNGSSRC 0.00% DNSUCE 0.00% FIVETENSINGLE 0.00%
The WEIGHT10 and WEIGHT20 tests are a weighting system that assigns a weight to each E-mail, based on the spam tests that fail, so they don't really count as spam tests by themselves (but, they show that you can catch as much as 98-99+% of spam with extremely few false positives). It is also important to note that different tests are more likely to produce false positives (such as the IPNOTINMX, XBL, REVDNS, and SPAMHEADERS tests, that all catch a lot of spam, but catch a lot of legitimate mail as well); those tests are best used in a weighting system, so E-mail will only be marked as spam if it fails a combination of tests. The NOLEGITCONTENT and IPNOTINMX tests were designed to help identify legitimate E-mail (rather than spam), which accounts for their high percentages.
Another interesting point is that about 50% of all spam can be caught with the BADHEADERS test, which will never catch any legitimate E-mail (unless it is sent from a non-RFC-compliant mail client). That's because so many spammers forge headers, and because spamware is typically written by people who do not know how to program well. Also worth noting is that over 40% of spam comes from "open proxies" (computers typically set up to cache web pages), and 33% of spam comes from IPs that are missing a reverse DNS entry.
There are 3 tests that catch over 90% of the spam in our spamtraps: SPAMMANAGER ( http://www.spammanager.com ) at 95.09%, SNIFFER ( http://www.sortmonster.com ) at 93.59%, , and SPAMCHK ( http://www.riedmann.it/spamchk/ ) at 95.73% (at its strictest setting; normally, a less strict setting would be used, to minimize false positives) .
More information on most of the spam tests shown above can be found at http://www.declude.com/junkmail/support/ip4r.htm . You can look up an IP address using the Spam Database Lookup tool at http://www.DNSstuff.com to see what spam databases it is listed in. The most recent 20 spams in our spamtraps, and the tests they failed, can be found at http://www.declude.com/spamtrap.htm .
-Scott
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