Exploiting the Trust Hierarchy among Email Systems
This paper presents a critique of the current status of the trust hierarchy found among SMTP based email systems. We evaluate current trends and present real evidence that the prevalence of ad-hoc initiatives for trust classification is a potential risk in itself. In that sense, we describe a vulnerability found in Google’s free email service (Gmail) that allows an attacker to exploit the current trust hierarchy that exists between email providers in order to assemble powerful spam/phishing attacks. We demonstrate this vulnerability by crafting a proof of concept attack software that is able to send whitelisted open relayed unlimited spam and phishing messages through Google’s email servers, thus giving concrete evidence of the presented threat.
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