Why your SPF project will fail
Having worked with many of Australia’s largest organisations to help secure their email ecosystem over the past 10 years, I’ve never seen so much hype about tackling Email Authentication than now. Whether that’s because of the exponential growth of domain spoofing or The Australian Signals Directorate’s Top 35 Cyber Mitigation Strategies, that recommended organisations deploy Email Authentication, there’s few organisations that aren’t at least considering deploying Email Authentication. But what is Email Authentication? Well, many organisations have been led to believe that SPF (Sender Policy Framework) will provide the domain resilience they need to ensure their email domains are locked down. SPF (Sender Policy Framework) was created back in 2002 as a protocol to eliminate unauthorised use of email domains. Now, pause for a moment and consider what other controls in the Security stack that were invented 15+ years ago have stood the test of time without adaptation or some form of evolution? Can’t think of any? Neither could I. Whilst SPF dramatically improved upon the inherently insecure platform that is Email, several fundamental flaws remained. And this forms the basis of why your SPF project will fail.
Flaw #1 – Correctly configured domains with an SPF record can still be spoofed
In an email, there are two “from” addresses. The envelope from (or “mail from”) and header from. SPF’s primary function was to validate the envelope from address, which is the “from” address that is invisible to the recipient. The header from address (what the recipient can see) can still be imitated without SPF failing. What’s worse, if for example the envelope from was badguy@dodgy.net, the domain owner could publish an SPF record and still display a header from of bob@acmecorp.net and successfully pass SPF.
Flaw #2 – SPF does not survive message forwarding
Over time, many consumer mailboxes have been configured with forwarding rules to deliver email to another mailbox. Unfortunately, a limitation of SPF is that when a message is forwarded, the originating IP’s are altered, rendering the SPF record invalid and therefore failing SPF. This can result in loss of legitimate emails intended for your recipients.
Flaw #3 – SPF Implementations are restricted to a maximum of 10 DNS lookups
The RFC that governs the SPF standard has placed a limit on the number of included DNS lookups that an SPF record can contain, restricting the total number of lookups to a maximum of 10. The use of ‘include’ statements, as well as ‘mx’ and ‘a’ records in an SPF entry allows an organisation to approve additional senders as defined in a third party’s SPF record. However due to the nested nature of these ‘include’ statements, particularly within your SPF record, simply including a single third party’s SPF record can in actual fact result in a multiplier effect of sorts, where that third party’s own SPF record consequently includes multiple additional DNS lookups of its own. This problem is commonly encountered where an organisation includes Outlook’s SPF record, which in turn includes a further 2 look-ups of its own.
It’s easy to see how the DNS lookup limitation is quickly reached, and critically important to understand the risks that this limitation presents. Most notably, the RFC for SPF specifies that if this limit is exceeded, it must result in a ‘PermError’, effectively meaning that even if your SPF record is currently set to ‘SoftFail’, receiving email gateways will automatically treat this record as a ‘HardFail’, potentially rejecting a significant volume of legitimate email. Additionally, the potential exponential scaling of the resulting DNS requests associated with these lookups can be exploited as part of a DOS or Amplification attack, while also resulting in excess bandwidth and memory utilisation in some cases.
Flaw #4 – SPF lacks visibility, resulting in potential (and likely) loss of business email
A modern businesses email environment is complex. Typically, the list of applications that are approved to send email on your behalf quickly runs into the dozens. But what happens when those systems (some of them owned and managed by third parties) change their IP address? What happens when the business (or shadow IT) decides to acquire a new platform for ad-hoc customer alerts or notifications? Email originating from these applications will fail SPF, but it may be some time before anybody realises, costing your business time and money.
————–
The net result from the above limitations of SPF is that for many organisations, the Email Authentication project loses momentum and quickly falls into the too hard basket. This is evidenced by the results of our analysis of the 5200 Australian organisation domains that currently have SPF, where we have found that over half have a fail open SPF record.
It’s not all bad news. In 2004, DKIM (DomainKeys Identified Mail) was created to authenticate an email through Cryptographic Authentication. And much later, in 2012, a collaboration between PayPal, Yahoo and other leading mail senders and receivers, saw the development of DMARC (Domain-Based Mail Authentication Reporting & Compliance). DMARC addresses and plugs the gaps that existed in SPF and DKIM, and adds visibility and control. DMARC is an open standard for authenticating email, which when done correctly, can eliminate Email Fraud for an organisation.
InfoTrust specialises in securing the email ecosystem and is actively evangelising the use of DMARC, alongside SPF and DKIM across the Asia Pacific Region to solve Email Fraud as an issue for businesses and Government. Here’s some of the brands that have already implemented DMARC to protect their brand and customers from Email Fraud.
For more information on DMARC, visit the InfoTrust Email Fraud page on our website or check back next week for our blog on DMARC.
see our
Related resources
Mimecast recently released its State of Email Security Report for 2021. The fifth edition of its annual report used interviews with over twelve hundred of information technology and cybersecurity professionals across the globe to gather vital cybersecurity insights. The report offers an insight into the latest email threats along with advice on how to build cyber resilience and mitigate the risks of email-borne attacks.
Cyber attacks and data breaches have been commonplace in the news headlines for some time now. Although a warning from the media is certainly helpful, there is so much more that can be done when it comes to threat intelligence sharing. Threat intelligence sharing is an important part of the global cybersecurity community effort to tackle cybercrime and should form a part of every organisation’s cybersecurity strategy. Sharing cyber threat intelligence enables organisations to make informed decisions about their cybersecurity, building more effective and robust cyber defences.
One of my favourite annual reports to read is the Verizon Data Breach Investigations Report. It’s packed full of insights about the threat landscape and security leaders, in my opinion, should read this report to get a pulse on what’s happening in cyber-scape.
After all, as cyber leaders, we are here to stop breaches – so the insights gained from real cyber incidents and breaches is gold in learning how to tighten up our defences.
All businesses, large and small, are under increasing pressure to demonstrate that they are managing the risk of cyberattacks. This means having the right processes and controls in place to identify risks and vulnerabilities, protect information, as well as detect, respond, and recover in the event of cybersecurity incidents. As such, many businesses are turning to certification authorities and security frameworks to demonstrate privacy and security best practice and achieve compliance with regulatory bodies. System and Organisation Controls (SOC 2) is one such compliance framework that can help organisations to create a structured approach to cybersecurity.
Frost & Sullivan has recently released its 2021 Frost Radar: Email Security report, where its findings provide a benchmarking framework to help businesses protect their email from cyber threats.
As we operate in an increasingly digital world, every business collect, store, and share more and more data. And, amongst that data is personal information. With the OAIC marking this year’s Privacy Awareness Week (PAW) from Monday 3 May to Sunday 9 May 2021, it’s time for us all to review how we protect our customers’ personal information.
We're Here To Help