Instead, there were loosely connected networks of mainframes and minicomputers managed by professional IT personnel running a variety of network protocols ( RFC 791, defining IPv4, was only released two (2) months before SMTP and TCP/IP had just begun its global rollout). This assumption made sense in 1981: The Internet as we know it didn’t exist yet. The SMTP protocol was designed with the assumption that every computer sending an email across a network could be trusted to provide accurate sender information. Nearly universal reliance on a protocol from a very different era is the root of today’s email spoofing problem. It is still possible to send an email to a modern mail server using the original 1981 version of the protocol. Modern ESMTP, defined in RFC 1869, has a variety of features and extensions that the original 1980s version of SMTP didn’t have but fundamentally operates the same way.
ESMTP is descended from the Simple Mail Transfer Protocol (SMTP), defined by RFC 788 in November 1981.
Take a Trip Through TimeĮmail moving between organizations on the Internet today uses the Extended Simple Mail Transfer Protocol (ESMTP) and various extensions that add features to the protocol. Spoofed emails include messages that appear to be from another organization or external emails that appear as if they came from inside an organization. Spoofed emails with forged sender information are a major problem as they can help phishing emails appear more realistic and bypass email filters. In this post, we will take a deeper dive into why email sender addresses are so easy to forge and show how it’s done. I briefly mentioned how easy it is to forge email sender addresses in a previous blog post that described the steps I took to determine whether a suspicious email was legitimate or a phishing attempt. By Chris Camejo in Attack Path Effectiveness Review, Business Risk Assessment, Incident Response, Incident Response & Forensics, Office 365 Security Assessment, Penetration Testing, Program Assessment & Compliance, Security Program Management, Security Testing & Analysis
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