Department of Computer Sciences The University of Texas at Austin Zmail : Zero-Sum Free Market...
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![Page 1: Department of Computer Sciences The University of Texas at Austin Zmail : Zero-Sum Free Market Control of Spam Benjamin J. Kuipers, Alex X. Liu, Aashin.](https://reader035.fdocuments.net/reader035/viewer/2022072013/56649e6b5503460f94b6a36f/html5/thumbnails/1.jpg)
Department of Computer Sciences
The University of Texas at Austin
Zmail : Zero-Sum Free Market Control of Spam
Benjamin J. Kuipers, Alex X. Liu,
Aashin Gautam, Mohamed G. Gouda
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The University of Texas at Austin 2
Spam Problem
Volume of Spam─ 2001: 8% of all email traffic was spam
─ 2004: 60% of all email traffic was spam
─ # emails per day: 31 billion (60% spam = 18.6 billion)
─ # spam emails per person per day = 6
Cost of Spam─ 2003: $10 billion/year in U.S. (Ferris Research)
$20.5 worldwide (Radicati Group)
─ Just cost for adding spam processing servers
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The University of Texas at Austin 3
Anti-Spam: Legal Approaches
Punish spammers by anti-spam laws
Problems─Hard to define spam
● First Amendment Right to Free Speech
─Hard to enforce anti-spam laws● Spammers move to another country
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The University of Texas at Austin 4
Anti-Spam: Filtering Approaches
Filter out spam based on text content
Problems─False Positive
● What if a job offer email gets filtered?
─Can be foiled by spammers● For example, imbedding spam text in images
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The University of Texas at Austin 5
Anti-Spam: Economic Approaches
Require senders to pay something
Human Effort: Sender pays human effort─ Inconvenient─ Inefficient─ Challenge can be perceived as rude
Computational Cost: Sender pays CPU time─ Inefficient
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The University of Texas at Austin 6
Anti-Spam: Zmail
Current cost for spamming is almost zero User’s attention is the important resource
consumed Basic idea of Zmail:
─ The sender of an email pays money directly to the receiver.
─ Zero sum (unlike USPS): The amount of money charged to the sender
=The amount of money rewarded to the receiver
─ The money earned can be used to send email.
─ The cost of sending one email is a unit called an e-penny.
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The University of Texas at Austin 7
Impact of Market Forces
Spammers─ Cost of spamming significantly increases─ Bulk email advertising become more targeted
Normal Users─ Most users receive more email than they send─ If not, pay money or subscribing commercial email
ESPs (Email Service Providers)─ Less spam, less bandwidth, less computational cost
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The University of Texas at Austin 8
Zmail Architecture
ESP ESP
ESP
User
User
User
User
User
User
User
Bank
User
User
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The University of Texas at Austin 9
The Zmail Protocol: two parties Bank:
─ Each compliant ESP has an account with bank─ Manage accounting for compliant ESPs─ ESP buy and sell e-pennies with bank─ Exchange e-pennies between real money for ESPs
ESPs:─ Manage accounting for each of its users─ Users buy and sell e-pennies with their ESPs
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The University of Texas at Austin 10
The Zmail Protocol: Email Transfer
An email: user s of ESP A user r of ESP B
Sending:─ A reduces s’s balance by one─ A records that A owes B one more e-penny
Receiving:─ B increments r’s balance by one─ B records that A owes B one more e-penny
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The University of Texas at Austin 11
The Zmail Protocol: Misbehavior Detection
What if an ESP lies?
Periodically, every ESP reports to the bank how much they owe to every other ESPs
Misbehavior Detection
─ A says that A owes B x e-pennies
─ B says that A owes B y e-pennies
─ If x != y, then Bank further investigates who lies.
─ Most ESPs are honest.
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The University of Texas at Austin 12
Mailing Lists
List server: email distributor + subscriber DB A subscriber sends an email to distributor, distributor forwards
the email to everyone Solution: for each email from distributor, receiver’s ESP sends
back an ack email.
Extra benefit: subscriber DB is always updated
Distributor Sender
1
2
100
-1+1+1
+1
+1
-100-1
-1
-1
+100
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The University of Texas at Austin 13
Zombies and Email Viruses
Zombie: sends out spam at user’s expense
Virus: sends email to everyone in address book
Solution: each user specify a limit on the number of email that he can send a day.
Extra benefit: detecting virus and zombies
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The University of Texas at Austin 14
Incremental Deployment
Zmail runs on top of SMTP
No change to SMTP
Deployment: starting from two compliant ESPs
A user may decide to segregate, filter, or discard email from non-compliant ESPs.
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The University of Texas at Austin 15
Bank Setup
Internet already has some central authorities such as IANA that controls IP assignment
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The University of Texas at Austin 16
Conclusions
Zmail gives no free ride to spammers
Zmail requires no definition of spam
Zmail works with other anti-spam techniques
Zmail can be incrementally deployed