1. Copyright © 2000, ZipLink Inc. Patent Pending 1 Mail Message Metering or, how to block outbound spam Robert D. Haskins

2. Copyright © 2000, ZipLink Inc. Patent Pending 2 Interactive Week, 3/6/2000 “… (Lawlor) opened AGIS to unsolicited commercial e-mailers and only relented after a walkout of key technical staff and a crippling hack attack in 1997.”

3. Copyright © 2000, ZipLink Inc. Patent Pending 3 Outline Introduction/Goals Problem definition Existing solutions Outline of our solution RADIUS database Mail relays Shortcomings References

4. Copyright © 2000, ZipLink Inc. Patent Pending 4 Wholesale Internet connectivity provider Our customers are free ISP’s, small ISP’s, and information appliance vendors (500+) ZipLink can be a source of spam Problem: an effective way to block outbound spam Solution: ? Introduction

5. Copyright © 2000, ZipLink Inc. Patent Pending 5 Goals Block at least 50% of outbound spam Little or no impact on customer (ISP) and subscriber Ability to exclude certain domains Configurable and scalable Low impact on RADIUS servers Utilize freely available software if possible

6. Copyright © 2000, ZipLink Inc. Patent Pending 6 Existing “free” solutions for spam: –Blackmail by Ken Hollis and James Murray –SMAPD from Trusted Information Systems –SMTPD from Obtuse Systems Corporation Brightmail by Bright Light Technologies RAS filters Existing solutions

7. Copyright © 2000, ZipLink Inc. Patent Pending 7 Existing solutions (2) No solution met our needs completely Most solutions are focused on the problem of inbound spam only No solution incorporates the idea of “message metering” Our solution: allow end user to send only X messages during Y amount of time

8. Copyright © 2000, ZipLink Inc. Patent Pending 8 Overview of solution SQL DBRADIUS User Mail RelayRecipient

9. Copyright © 2000, ZipLink Inc. Patent Pending 9 RADIUS servers run radius2db, written by Dale Nielsen (contractor) in C radius2db reads RADIUS accounting logs and forwards records to Oracle database overhead on RADIUS server < 5% additional fields for message counts, limits in separate table RADIUS database

10. Copyright © 2000, ZipLink Inc. Patent Pending 10 Mail Relays User sends mail Mail sent to recipient SMTP redirected Mail relay quota check Cust. mail relay

11. Copyright © 2000, ZipLink Inc. Patent Pending 11 Modifications made to SMTPD (Obtuse) SMTPD receives outbound message: –verifies source IP address within ZipLink range –checks mail quotas for that user –forwards message to SMTPFWD SMTPFWD relays message (via Sendmail) to ISP customer mail relay for final delivery Mail Relays (2)

12. Copyright © 2000, ZipLink Inc. Patent Pending 12 Adjustable parameters: –# messages/time interval for user@realm –# messages/time interval for @realm –# messages/time interval, global –10 messages/10 minutes, max 100 messages/24 hours is the compiled in default “450 Mail quota exceeded for %U” error Mail Relays (3)

13. Copyright © 2000, ZipLink Inc. Patent Pending 13 Shortcomings Still requires Acceptable Use Policy (AUP) and strong language in contracts If ISP changes defaults, subscriber can still spam if thresholds are set high enough No way to allow individual subscriber to use 3rd party mail relay Requires mechanism for redirecting all SMTP sessions to mail relays

14. Copyright © 2000, ZipLink Inc. Patent Pending 14 My page: www.ziplink.net/~rhaskins FWTK: www.tis.com/research/software Blackmail: bitgate.com/spam Juniper/smptd: www.obtuse.com/smtpd.html Brightmail: www.brightlight.com/isp/spam References