Anti-Spoofing for Email Gains Adoption, but Enforcement Lags

The number of domains using an anti-spoofing technology known as Domain-based Message Authentication, Reporting, and Conformance, or DMARC, topped 2.7 million in 2020, yet most domains still fail to specify a policy to delete or quarantine unauthenticated email, according to data from security firms published over the last month.

During the pandemic, email scams and phishing attacks that purported to be from the World Health Organization (WHO) widely targeted businesses and government agencies. DMARC foils one component of such attacks, when the attacker spoofs an organization in an e-mail's From field. As of December 2020, more than 2.7 million domains published a DMARC record, up 43% during the last year, according to the latest adoption report on DMARC.org, based on data from Farsight Security, a cybersecurity intelligence firm.

Still, two-thirds of those domains do not specify any policy for unauthenticated email, instead essentially monitoring the situation, according to the Farsight data. With ransomware and non-spoofed phishing attacks increasingly common, companies are tackling those issues that have the most impact on their risks, says Ben April, chief technology officer for Farsight Security.

"We will continue to see it slowly creep up for a while," he says. "It's a trickle of adoption mainly based on companies asking, 'What is going to kill me next?' That sort of risk analysis determines what important threats the company needs to focus on next."

DMARC allows an organization to specify how recipients should handle unauthenticated messages using information inserted into its domain-name record. Using two other standards — Sender Policy Framework (SPF) and Domain Key Identified Mail (DKIM) — for verifying the authenticity of a message and checking whether the source is authorized to send email messages, the recipient has all the necessary information to check the source of email and apply the DMARC policy.

With email playing a role in more than half of malware attacks and phishing the most common vector in breaches, according to the "Verizon Data Breach Investigations Report (DBIR)," securing business messaging is a top priority.

Overall, the numbers suggest that the email authentication technologies continue to grow as a standard, but while necessary, they are not sufficient, says Olesia Klevchuk, a senior spokesperson for cybersecurity firm Barracuda Networks.

"Initially, it was primarily brand-conscious organizations adopting, but we are now seeing broader adoption as good security hygiene," she says. "As a security control, it's a good step, but nowhere near sufficient to protect against sophisticated phishing."

Domains that use DMARC are less likely to be sources of suspicious email messages, with 1.9% of messages from non-DMARC domains considered suspicious, compared with only 0.4% of messages from domains enforcing DMARC, according to a report by email security provider Valimail. In its own data, the company found that nearly 1.3 million organizations have added email authentication information to their domain as a way to fight spoofing, but less than 15% strictly enforce the policy.

Other research, such as this 2018 USENIX paper, found that about 60% of domains with a mail server had an SPF record and only 6% specified a DMARC policy. 

Yet volume matters as well. The absolute number of domains hides the fact that adoption by the most major sources of email — such as Google, Microsoft, Apple, and others — is a more important factor.

As far back as 2013, Google boasted that the adoption of SPF and DKIM had reached high levels. More than 95% of email messages came from an email server with an SPF record, and almost 87% have a server with a DKIM record, the company stated in an updated 2016 blog post, which represents the latest data released by the company.

While the adoption of the technologies has made it harder for attackers, they are finding ways around it, says Barracuda's Klevchuk.

"Although hackers still use domain spoofing as a tactic — especially when DMARC is not configured properly — they are increasingly turning to domain impersonation, [where] attackers attempt to impersonate the domain of a legitimate business by using techniques such as typosquatting," she says. "As more organizations start to adopt DMARC, hackers will start to turn more to tactics such domain impersonation to get through existing email security."

Story updated on March 25.