Microsoft Criticised By UK’s Cyber Security Agency Over Dmarc

The UK’s National Cyber Security Centre (NCSC) has complained that it has been unable to compile meaningful statistics and draw meaningful conclusions about email security in its latest report because Microsoft stopped sending Dmarc reports two years ago.

What Is Dmarc?

Domain-based message authentication, reporting and conformance (Dmarc) is a protocol, developed by the Trusted Domain Project, to help provide greater assurance on the identity of the sender of a message, and it builds upon the email authentication technologies SPF and DKIM developed over a decade ago and the work on a collaborative system pioneered by PayPal Yahoo! Mail and later Gmail. 

Dmarc allows email and service providers to share information about the validity of emails they send to each other, including giving instructions to mailbox providers about what to do if a domain's emails aren't protected and verified by SPF and/or DKIM e.g. moving a message directly to a spam folder or rejecting it outright. Information about messages that have passed or failed DMARC evaluation is then fed back to a DMARC register, thereby providing intelligence to the sender about messages being sent from their domain and enabling them to identify email systems being used by spammers.

Dmarc works on inbound email authentication by helping email receivers to determine if a message “aligns” with what the receiver knows about the sender and if not, Dmarc includes guidance on how to handle the “non-aligned” messages e.g. phishing and other fraudulent emails. 

Why Were Microsoft’s Dmarc Reports So Important?

Microsoft’s email platforms form one of the biggest receivers of email, and data from Microsoft about the number of emails failing Dmarc gives a good indication of the number of suspicious emails being sent.  The lack of this data in the NCSC’s Mail Check service means that the NCSC’s ability to monitor and report on email security driven by Dmarc adoption has been hampered. This blind spot could have a knock-on negative impact on email security for everyone.

Public Sector Uptake – Good News

The NCSC’s latest report contains good news, however, about a significant uplift in the public sector adoption of email security protocols.  For example, public sector domains using Dmarc more than tripled from December 2017 to December 2018 to 1,369, and the number of domains with a Dmarc “quarantine” or “reject” policy (to prevent suspicious emails being delivered to inboxes) also tripled.

What Does This Mean For Your Business?

Having a collaborative intelligence sharing and effective protocol and process such as Dmarc that is being widely adopted by many organisations has significantly improved email security.  This is particularly valuable at a time when businesses face significant risks from malicious emails e.g. phishing and malware, and email is so often the way that hackers can gain access to business networks.

Sharing intelligence about the level and nature of email security threats and how they are changing over time e.g. in the trusted NCSC report, is an important tool to help businesses and security professionals understand more about how they tackle security threats going forward.  It is, therefore, disappointing that one of the world’s biggest receivers of email, which itself benefits from Dmarc, is not providing reports which could be of benefit to all businesses and organisations.