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Posts Tagged ‘STS’

Stronger Email Security with SMTP MTA STS: Strict Transport Security

Wednesday, July 25th, 2018

Email transmission between servers has historically been extremely insecure.   A new draft internet standard called “SMTP Strict Transport Security” or “SMTP MTA STS” is aiming to help all email providers upgrade to a much more secure system for server-to-server mail transmission.    This article lays out where we are currently in terms of email transmission security and how SMTP MTA STS will help.

Email servers (a.k.a. Mail Transmission Agents or “MTAs”) talk to each other using the Simple Mail Transmission Protocol (SMTP). This protocol, developed in 1982, originally lacked any hint of security. As a result, a lot of the email shooting around the internet is still transmitted in plain text.  Its easily eavesdropped on, easily modified, untrusted and not private.

SMTP MTA STS

Back in 2002, an extension to SMTP called “STARTTLS” was standardized.  This extension permitted servers to “upgrade” SMTP communications from plain text to an encrypted TLS-secured channel, when both servers supported compatible levels of TLS.  This process is known as SMTP TLS. In principle, this security addition was really great.  The “TLS” used is the same encryption method used by your web browsers to talk to secure web sites (e.g., banks, Amazon, your email provider, etc.).  Your web browsers do relatively good job making sure that connections to these secure sites are safe.  I.e., they seek to ensure that there is encryption, that the encryption is sufficiently strong, and that there is no one actively eavesdropping on your connections.

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ARC and SMTP MTA-STS: The State of Domain-based Email Authentication – Part 3

Tuesday, September 19th, 2017

We’ll close (for now) our three part series on the state of domain-based authentication for emails by completing the story on technologies being deployed or defined to improve the security of the email ecosystem. In Part 1, we wrote about using Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) to authenticate the sending mail server. Part 2 described how Domain-based Message Authentication, Reporting and Conformance (DMARC) is used to provide clear guidelines for the treatment of mail that fail SPF and/or DKIM authentication.

Authenticated Received Chain

In this post, we’ll touch on two topics that are mature works in progress in the IETF, the technical standardization organization that has brought us so much of the protocols that govern the internet. The first technology is Authenticated Received Chain (ARC), defined to handle the shortcomings of SPF and DKIM when used with mail forwarders or mailing lists. The second technology is about correcting the lack of security between Message Transfer Agents (MTA), and a solution to enforce strict transport layer security for SMTP message transfer between MTAs.

It’s worth reiterating again that all these technologies are building blocks, and only when used and deployed collectively by the entire ecosystem can we hope to create the barriers needed to thwart fake emails and mail surveillance by malicious actors.

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