Protection Against Spam Using Pre-Challenges

Abstract

Abstract:Spam turns out to be an increasingly serious problem to email users. A number of anti-spam schemes have been proposed and deployed, but the problem has yet been well addressed. One of those schemes is challenge-response, in which a challenge is imposed on an email sender. However, such a scheme introduces new problems for the users, e.g., delay of service and denial of service attacks. In this paper, we introduce a pre-challenge scheme that avoids those problems. It assumes each user has a challenge that is defined by the user himself/herself and associated with his/her email address, in such a way that an email sender can simultaneously retrieve a new receiver's email address and challenge before sending an email in the first contact. Some new mechanisms are employed to reach a good balance between security against spam and convenience to email users.

Enforcing Email Addresses Privacy Using Tokens

“…The idea is that an already publicly known challenge (which changes periodically) has to be solved to be able to send a message. This reduces the number of required messages between recipient and sender to one like in normal email [6]. SPA: A concept proposed by John Ioannidis from AT&T Labs called SPA (Single-Purpose Address) [9] is in fact quite similar to the concept proposed in this paper.…”

An effective multi-layered defense framework against spam

“…This is our main protection against spam at the client-level (Roman et al, 2005). Each email user will define a challenge exclusively for his/her email address.…”

“…When a combination of anti-spamming methods is used jointly in a layered structure, we can improve on the efficacy of spam filtering while reducing the number of false positives. We implemented a sub-system using our pre-challenge method (Roman et al, 2005). A prototype is built as an add-on in Microsoft Outlook 2002.…”

A Trust Based System for Enhanced Spam Filtering

“…Another idea is to require the sending client to solve a computational challenge for each message, greatly slowing bulk mail generation. Other techniques include issuing of cryptographic challenges that rely on message history between the parties (to get around address spoofing) [9] and the use of prechallenges [10]. Additional tricks, such as obfuscation of published email addresses and the use of human interactive proofs [11] in email account creation systems, try to frustrate spammers by making it harder to automate their activities.…”