Page 24 - Cyber Defense eMagazine - October 2017

“DMARC” for short. Within its first year, 60% of internet mailboxes used DMARC verification for
anti-spam and anti-phishing.

DMARC allows a message sender’s domain to advertise if their messages should be protected
by SPF and/or DKIM, and provides instructions to recipient mail servers for what to do if a
message fails these checks. Along with the normal SPF and DKIM checks, DMARC also checks
if the envelope MAIL FROM header matches the message’s FROM header.

DMARC assumes that the domain administrator has already configured DKIM and SPF for their
sending domain. DMARC then uses a DNS TXT record, just like SPF and DKIM, to verify
important information for the sending domain. The DMARC DNS record includes a policy for the
recipient mail server to apply when DKIM and/or SPF records fail, such as rejecting the
message, quarantining it, or allowing it through, and an email address to send reports to for
non-compliant messages.

DMARC fills in the gaps left over from SPF and DKIM, providing additional anti-spoofing
protections and directions for recipient mail servers on how to handle potentially spoofed
messages. A recent report by ValiMail and the Global Cyber Alliance found 76% of email
inboxes now support DMARC verification. Unfortunately, according to a recent report by Return
Path, DMARC implementation is still very low in most verticals, ranging from 16% (Healthcare)
at worst to 61% (Payment Services) at best.
To find out why these anti-phishing standards aren’t more widely used and what might be done
to increase their adoption, check back for Part II next month.

About the Author

Marc Laliberte is an Information Security Threat Analyst
at WatchGuard Technologies. Specializing in networking
security protocols and Internet of Things technologies,
Marc’s day-to-day responsibilities include researching
and reporting on the latest information security threats
and trends. He has discovered, analyzed, responsibly
disclosed and reported on numerous security
vulnerabilities in a variety of Internet of Things devices
since joining the WatchGuard team in 2012. With
speaking appearances at industry events and regular
contributions to online IT, technology and security
publications, Marc is a thought leader who provides
insightful security guidance to all levels of IT personnel.

24 Cyber Defense eMagazine – October 2017 Edition
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