Reduce your SPAM in 5 easy steps, guaranteed!

Running your own mail server can be a great experience, but the ever-looming threat of SPAM can suck the fun right out of it and make you wonder if moving your mail server to Google Mail or some other service would be better. IN this short tutorial, Craig Maloney will show several easy techniques you can put into place today in order to keep your mail server from accepting SPAM. He’ll also touch briefly on the SPF protocol and how you can help lower SPAM back-scatter, and help get your mail through witl little hassle. We’ll also cover why Bayesian Spam Filtering and Greylisting are overkill for a problem that can be easily addressed on a low-powered machine. Get your mail queue back, and take back your resources, guaranteed, or your money back.

Transcript

1. “I Get Low Spam” (Or: How to run your own mail server, get low spam, and not have to run a Bayesian filter) Craig Maloney Michigan!/usr/group 2013-03-12
2. The Problem... http://www.flickr.com/photos/the_justified_sinner/2498066986/sizes/o/
3. But there's always Web Mail... http://www.flickr.com/photos/sin_agua/2091072379/sizes/o/
4. We're UNIX-folk. We can do better. (For starters, we can stop using Comic Sans in our presentations)
6. “I Get Low Spam” (Note: not “no SPAM”) Guaranteed Results In 10 days or your money back!!1!
7. 5 easy steps to low SPAM 1) Postfix 2) DNS Lookups 3) ZEN – Spamhaus 4) Spamcop (bl.spamcop.net) 5) SPF Lookups Note: SpamAssassin or other Bayesian SPAM filters need not apply
8. Postfix http://www.postfix.org
9. DNS Lookups http://www.flickr.com/photos/skimaskdude/4379613766/sizes/l/ (Does your domain name map to a real address)
10. ZEN - Spamhaus • Part of the Spamhaus project • Combines several of their services • Free for individuals and non-profit organizations • Checks if sender's domain is blacklisted http://www.flickr.com/photos/bermilabs/4078685721/
11. bl.spamcop.com • Blacklist for known bad domains • Straight blacklist of domains. • Run by Cisco • (Has a reporting service if you're into that sort of thing) http://www.flickr.com/photos/freefoto/2194435381/sizes/o/
12. SPF – Sender Policy Framework • (Hint: The S doesn't stand for “Simple”) • Uses DNS to help validate sender identity • http://openspf.org For help on setting up SPF as a mail sender. • http://www.kitterman.com/spf/validate.html (you will use this to validate your SPF record) • SPF Install instructions for Ubuntu: – https://help.ubuntu.com/community/Postfix/SPF
13. SPF – Sender Policy Framework SPF record lookup and validation for: decafbad.net SPF records are primarily published in DNS as TXT records. The TXT records found for your domain are: v=spf1 a mx ~all SPF records should also be published in DNS as type SPF records. No type SPF records found. Checking to see if there is a valid SPF record. Found v=spf1 record for decafbad.net: v=spf1 a mx ~all evaluating... SPF record passed validation test with pySPF (Python SPF library)!A
14. SPF – Sender Policy Framework • Things to keep in mind about SPF – SPF validates the address of the server is valid to send for the server's domain, NOT the FROM: domain – Validate, Validate, Validate – Examples for various domains: • http://www.openspf.org/FAQ/Examples
15. Postfix configuration smtpd_recipient_restrictions = reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unauth_pipelining, permit_sasl_authenticated permit_mynetworks reject_unauth_destination check_policy_service unix:private/policy-spf reject_rbl_client zen.spamhaus.org, reject_rbl_client bl.spamcop.net, check_sender_access hash:/etc/postfix/sender_access
16. Sender Access http://www.flickr.com/photos/andrewscott/3966092912/sizes/o/ Polite way of telling mis-configured mailing bots to please go away.
17. Parting thoughts • Mailing lists – convenient ways for getting SPAM – Unsubscribe from those you no longer read. – Mailing list owners will get SPAM. I'm sorry. • DKIM – Domain-keys identified mail. Requires crypto. • DMARC: – Combines SPF and DKIM together • Messages pass SPF and / or DKIM checks and “alignment”.
18. Parting thoughts (cont.) http://www.flickr.com/photos/rainbirder/7011735065/sizes/o/ None of this prevents Phishing None of this prevents Phishing
19. Questions? http://www.flickr.com/photos/22320444@N08/5270166802/sizes/m/
20. Thank you! http://www.flickr.com/photos/barmala/2561602478/