No Effective Spam Solution?

[consultant]

I've personally found the challenge-response third party spam filters to be by far the most effective. I realize the selfish aspect of using one of these services as they multiply the amount of undelierable e-mail floating around with all the auto-repsonse challenge message.

So I'm working with a company of 20 employees that wants to reduce their spam. We installed SpamAssassin on their server (Pleask 7.5 Reloaded.) It hasn't identified a single spam message. The reason is all the spammers know exactly how to craft the e-mail to avoid the filter. Many of the e-mails that get through are just an image file with the text in it. Other's are plain text messages where any trigger words are intentionally misspelled. It appears these content-based filters like SpamAssassin or the 4PSA product are more or less useless from the aspect of providing any *significant* amount of SPAM reduction. Maybe they'll catch a message or two here and there but in large part, the spammers are way ahead of these guys. So that leads back to challenge-response really being the only *significantly* effective solution. It gets ALL my spam, and maybe 1 in 25 legitimate senders are too stupid, paranoid, or lazy to respond to the challenge so I periodically scan the junk folder and whitelist them.

If you count out the Challenge-Response method of SPAM filtering, the only other effective option is to simply change your e-mail address periodically and be careful what forms you put it on. I have several "disposable" addresses I use when I suspect I could end up on a list.

Is Challenge-Response really so bad? Is there a content-filter based SPAM solution out there that REALLY works and if so what is the typical percentage of SPAM it is currently catching on your server?

 

[Galactic Zero]

Have you looked at adding Rules du Jour? I've been running that and so far it has caught 98% of the spam. If you haven't yet looked at AtomicRocketTurtles.com website at the anti virus/spam section you probably need to.

My current setup is RHEL 3, PSA 7.5.3, Spamassassin from ART's repo, ClamAv from Dag's repo, psa-spamassassin 7.5.4, Pyzor, Rule du Jour with these filters, portion of my mail header follows:

X-Spam-Flag: YES
X-Spam-Checker-Version: SpamAssassin 3.1.1 (2006-03-10) on gz.galacticzero.net
X-Spam-Level: *************************
X-Spam-Status: Yes, score=25.3 required=7.0 tests=BAYES_80,
RCVD_IN_BL_SPAMCOP_NET,RCVD_IN_DSBL,RCVD_IN_NJABL_PROXY,
RCVD_IN_SORBS_SOCKS,RCVD_IN_SORBS_WEB,RCVD_IN_XBL,UNPARSEABLE_RELAY,
URIBL_JP_SURBL,URIBL_OB_SURBL,URIBL_SBL,URIBL_WS_SURBL autolearn=spam
version=3.1.1

 

[atomicturtle]

Theres certainly no silver bullet in anti-spam systems. Personally, email challenge-response systems evoke a level of vitriolic hatred on my part that I can only compare to the disgust I feel toward alpacas, or the fat kid on season 2 of "CHiPs".

You either love it or hate it, I suppose. Then I think you go around trying to convince other people to love it or hate it.

 

[sieb@]

I use a seperate server on the frontend to filter all the spam before it gets to the hosting servers. Its MailScanner with MailWatch, MailScannter-MRTG, and BitDefender scanner. It gets 70-90% depending on how many total messages come through that day. Fort Systems has a mailscanner (same setup but with their own web frontend) that I used with much success before I built this. This lightens the load on my hosting servers and lets the users set stricter spam settings if they like.

 

[atomicturtle]

Yep I do the same thing with Project Gamera (http://www.atomicrocketturtle.com/Joomla/content/view/77/29/)

If you look at the bottem of the page I've been making notes on tuning that type of configuration, as well as spamassassin in general.