Top website domains are vulnerable to email spoofing

Email spoofing — a common tactic of spammers — basically involves forging the sender’s address. Messages can appear as if they came from Google, a bank, or a best friend, even though the email never came from the actual source. The spammer simply altered the email’s "from" address.

Authentication systems have stepped in to try and solve the problem. But many of the top website domains are failing to properly use them, opening the door for spoofing, according to Sweden-based Detectify, a security firm.

The company analyzed the top 500 websites ranked by Alexa and found that 276 of the domains are vulnerable as a result, it said in a blog post on Monday.

Of those vulnerable, 40 percent were news and media sites, and 16 percent were software-as-a-service sites, Detectify said in an email.

A common way these domains are trying to prevent email spoofing is through a validation system called Sender Policy Framework or SPF. It essentially creates a public record, telling the Internet which email servers are allowed to use the domain. Ideally, any messages impersonating the domain will be detected as spam and rejected before delivery.

In practice, however, the system can often come up short. The SPF will filter out spam emails best when on the so-called "hardfail" setting, but many website domains decide to implement the SPF at the "softfail" level. Although this will flag any forged emails as suspected spam, the messages will still be sent out to the recipient.

Companies in charge of the website domains do this to avoid losing legitimate emails that might be falsely flagged, said John Levine, a long-time email infrastructure consultant.

“There are a lot of ways to send mail legitimately, and SPF can only describe some of them,” he added.

Email providers such as Gmail can also skip marking any messages as spam, even if an SPF system softfail was used, Detectify said.

The 276 web domains found vulnerable were using no SPF system or had set their SPF system on softfail. Others had misconfigured their email validation systems to do nothing when detecting spam, Detectify said.

Companies in charge of these domains are either unaware of the problem, or assume they’re already protected, Detectify said. Enacting better email validation systems can also be complicated, and some companies don’t see it as a priority.

"Many people falsely think they’re protected using SPF only," Detectify added. The security firm is advising companies use a newer email validation system, called DMARC (Domain-based Message Authentication, Reporting & Conformance) to prevent the problem.

DMARC is gaining wider adoption in the IT industry, including from Yahoo and Google. The protocol is essentially designed to streamline the process of email spoofing detection, but still not everyone is using it.

Detectify’s research found that only 42 percent of the top 500 sites in the world use DMARC.

Although DMARC is "far from foolproof," the system has been effective in preventing email-based attacks, Levine said.

For instance, phishing attacks against Paypal users may have dropped as a result of email providers adopting DMARC, security firm Kaspersky Lab said in 2015.