The Trouble With DMARC: 4 Serious Stumbling Blocks

Since its creation, email has suffered from an "original sin" - the inability to confirm a sender’s true identity. Recently, that flaw has led to an onslaught of phishing attacks - which often lead to further network compromise. According to one recent study, phishing is the launch vehicle for 91% of all cyberattacks.

In response, a growing number of organizations are turning to DMARC (Domain-based Message Authentication, Reporting, and Conformance), an open standard that can help prevent phishing attacks. As a critical additional benefit, DMARC also helps IT administrators get control over which cloud services are sending email on their behalf.

DMARC has been proven to be highly effective at both of these jobs, but we’re finding that a large number of companies are not successful at fully implementing DMARC. Recent data shows that DMARC usage is growing exponentially. But when ValiMail analyzed more than 1 million of the largest domains on the Web, we found that around 70% of those who implemented DMARC were not getting it right: Either there were configuration errors or DMARC was not actually switched on to enforcement mode. Just as surprising, the 70% failure rate applied to all companies, regardless of their size.

In other words, even with the near infinite IT resources of the largest companies in the world, they did no better than a mid-sized company when it came to properly implementing email authentication. Here’s why:

DMARC Is Tricky to Implement
The first problem is that DMARC is based on two 10-year-old standards, SPF and DKIM. All three standards are based on DNS TXT records, which is pragmatic (DNS is a great place to store domain-relevant information) but has an unfortunate downside in terms of configuration. DNS is the furthest thing from a point-and-click environment you can imagine. There is no GUI, the syntax is cryptic - you have to edit text records character by character - and the slightest error can screw everything up.

Complicating matters is the fact that DNS is so critical to the operation of an online business. Consequently, many organizations require a multi-week process before making any DNS record changes. With DMARC, SPF, and DKIM, you might be making many such changes as you configure and tweak your setup. Half a dozen DNS changes could easily take months to get through the pipeline.

DMARC Was Not Built for the Cloud Era
The DMARC standards themselves have built-in limits that make them challenging for companies that have embraced cloud services.

For instance, Sender Policy Framework (SPF) - an open, DNS-based email authentication system -  has a 10-domain lookup limit. SPF records are allowed to specify whitelisted servers by IP address or by rule sets included from other domains. But to protect against denial of service attacks, receiving mail servers won’t actually look up more than the first 10 rule sets listed in an SPF record. Since each cloud service typically uses between 3-5 rule sets, you’ll probably run into the 10 lookup limit with only three cloud services.

So if your company is using more than three cloud services that want to send email on your behalf, you need to list those cloud services’ mail servers by IP address. Do you know all the IP addresses used by Salesforce.com mail servers? How about Gmail? Are you prepared to update your DNS record every time one of those providers adds a new server?

No One Wants to Cut Off Critical Services Accidentally
Many companies lack the confidence that they’ve identified all the legitimate services that should be able to send email on their behalf. The consequences of an error can be high: Your IT guy might never have heard about Zapproved, and its message volume may be very low. But Zapproved is a legal discovery tool, and if you support a law firm and your attorneys are using it, cutting off its access to email could be disastrous for any legal work the firm has in progress.

IT administrators know the risks, so they are reluctant to take DMARC all the way to enforcement mode until they are absolutely sure it’s not going to cut off any critical services. Given the problems with DMARC’s complexity and its built-in limitations, that state of absolute confidence may never arrive.

Configuration Is Just the First Step
Now, consider that the above three problems -- DNS entries, standards limitations, and service identification -- all relate to configuration. That’s really only the first step. Once your email authentication is configured correctly and set to enforcement mode, you will need to consider maintenance, management, and alerting/notification (dealing with warnings, alerts to spikes in phishing attacks).

A lot of companies start with the best of intentions, thinking DMARC is an open standard, and not appreciating the complexity that comes with implementation. They then get into hot water and can’t get past the initial "monitoring mode" of DMARC without ever getting to enforcement, where DMARC’s greatest security and compliance benefits reside. It's an unfortunate reality that DMARC is simple in principle but complicated to manage in today's modern, cloud-centric world. The devil is in the details.

Related Content: