Check out the new USENIX Web site.
USENIX, The Advanced Computing Systems Association

NSDI '08 Abstract

Pp. 1530 of the Proceedings

Ostra: Leveraging Trust to Thwart Unwanted Communication

Alan Mislove and Ansley Post, Max Planck Institute for Software Systems and Rice University; Peter Druschel and Krishna P. Gummadi, Max Planck Institute for Software Systems


Online communication media such as email, instant messaging, bulletin boards, voice-over-IP, and social networking sites allow any sender to reach potentially millions of users at near zero marginal cost. This property enables information to be exchanged freely: anyone with Internet access can publish content. Unfortunately, the same property opens the door to unwanted communication, marketing, and propaganda. Examples include email spam, Web search engine spam, inappropriately labeled content on YouTube, and unwanted contact invitations in Skype. Unwanted communication wastes one of the most valuable resources in the information age: human attention.

In this paper, we explore the use of trust relationships, such as social links, to thwart unwanted communication. Such relationships already exist in many application settings today. Our system, Ostra, bounds the total amount of unwanted communication a user can produce based on the number of trust relationships the user has, and relies on the fact that it is difficult for a user to create arbitrarily many trust relationships.

Ostra is applicable to both messaging systems such as email and content-sharing systems such as YouTube. It does not rely on automatic classification of content, does not require global user authentication, respects each recipient's idea of unwanted communication, and permits legitimate communication among parties who have not had prior contact. An evaluation based on data gathered from an online social networking site shows that Ostra effectively thwarts unwanted communication while not impeding legitimate communication.

  • View the full text of this paper in HTML and PDF. Listen to the presentation in MP3 format.

    The Proceedings are published as a collective work, 2008 by the USENIX Association. All Rights Reserved. Rights to individual papers remain with the author or the author's employer. Permission is granted for the noncommercial reproduction of the complete work for educational or research purposes. USENIX acknowledges all trademarks within this paper.
To become a USENIX member, please see our Membership Information.

Last changed: 11 Aug 2008 mn