Good morning DMARC

I’m thinking I may need to deploy DMARC report automation sooner rather than later.

… and so on, and on, and on for a lot further down the mailbox.

Related Posts

Minimal DMARC

The intent of DMARC is to cause emails to silently vanish.
Ideally deploying DMARC would cause all malicious email that uses your domain in the From address, but which has absolutely nothing to with you to vanish, while still allowing all email you send, including mail that was sent through third parties or forwarded, to be delivered.
For some organizations you can get really close to that ideal. If you control (and know about) all the points from which email is sent, if your recipients are individuals with normal consumer or business mailboxes, their mailbox providers don’t do internal forwarding in a way that breaks DKIM before DMARC is checked and, most importantly, if your recipients are a demographic that doesn’t do anything unusual with their email – no vanity domain forwarding, no automated forwarding to other recipients, no alumni domain forwarding, no forwarding to their “real” mailbox on another provider – then DMARC may work well. As long as you follow all the best practices during the DMARC deployment process it’ll all be fine.
What, though, if you’re not in that situation? What if your recipients have been happily forwarding the mail you send to them to internal mailing lists and alternate accounts and so on for decades? And that forwarding is the sort that’s likely to break DKIM signatures as well as break SPF? And while everyone would advise you not to deploy DMARC p=reject, or at least to roll it out very slowly and carefully with a long monitoring period where you watch what happens with p-none, you have to deploy p=reject real soon now?
What can you do that’s least likely to break things, while still letting you say “We have deployed DMARC with p=reject” with a straight face?

Read More

Email pranks and spoofing

Earlier today a twitter user calling himself Email Prankster released copies of email conversations with various members of the current US administration. Based on his twitter feed, and articles from BBC News and CNN, it appears that the prankster forged “friendly from” names in emails to staffers.
A bunch of folks will jump on this bandwagon and start making all sorts of claims about how this kind of thing would be prevented if the Whitehouse and other government offices would just implement DMARC. Problem is, that’s not true. It wouldn’t have helped at all in this case. Looking at the email screenshots all of the mail seems to come from legitimately registered addresses at free email providers like mail.com, gmail.com, and yandex.com.
One image indicates that some spam filter noticed there may be a problem. But apparently SUSPECTED_SPAM in the subject line wasn’t enough to make recipients think twice about checking the email.

The thing is, this is not “hacking” and this isn’t “spear phishing” and it’s not even really spoofing. It’s social engineering, at best. Maybe.

Read More

About that DMARC "exploit"

A security researcher has identified a rendering flaw that allows for “perfect” phishing emails. From his website:

Read More