How to send mass e-mail the right way

Published: 2014-01-24
Last Updated: 2014-01-28 23:42:54 UTC
by Johannes Ullrich (Version: 1)
4 comment(s)

We all don't like spam, but sometimes, there are good reasons to send large amounts of automatically created e-mails. Order confirmations, newsletters or similar services. Sadly, I often see how it is done wrong, and would like to propose some rules how to send mass e-mails correctly. 

The risks of doing it incorrectly are two fold: Your e-mail will get caught in spam filters, or your e-mail will teach users to fall for phishing, endangering your brand.

So here are some of the rules:

- Always use an address as "From" address that is within your domain. Even if you use a third party to send the e-mail. They can still use your domain if you set them up correctly. If necessary, use a subdomain ("" vs "").
- Use DKIM and or SPF to label the e-mail as coming from a source authorized to send e-mail on your behalf. DKIM can be a bit challenging if a third party is involved, but SPF should be doable.  Using a subdomain as From address can make it easier to configure this. For extra credit, use full DMARC to setup e-mail addresses to receive reports about delivery issues.
- Use URLs only if you have to, and if you do, don't "obscure" them by making them look like they link to a different location then they actually do. Use links to your primary domain (subdomain as a work around).
- Try to keep them "plain text", but if you have to use HTML markup, make sure it matches the look and feel of your primary site well. You don't want the fake e-mail to look better then your real e-mail.
- watch for bounces, and process them to either remove dead e-mail addresses or find our about configuration issues or spam blocklisting quickly.

Of course, I would like to see more digitally signed e-mail, but I think nobody really cares about that. 

Any other ideas?

Johannes B. Ullrich, Ph.D.
SANS Technology Institute

4 comment(s)
Security Update for OS X for CVE-2014-1252

Phishing via Social Media

Published: 2014-01-24
Last Updated: 2014-01-24 14:07:39 UTC
by Chris Mohan (Version: 1)
1 comment(s)
The use of social media as an attack vector is nothing new; We’ve all seen plenty of stories in the media of fake FaceBook profiles such as the one for American Admiral James Stavridis back in 2012 [1]. This tends to mean we’re more wary of Facebook and Twitter, but many of us still use LinkedIn as it is a great tool to build out professional networks, tap in to like-minded groups or be stalked approached by recruiters.
If a LinkedIn request comes from a name you recognise, do you blindly except the request or do a bit of investigating first to validate that request? Let’s say you are the cautious, security minded type and check of the profile of the sender and it looks legitimate, I’m betting most of us would then accept the request and get on with our day.
The last couple of Diaries I’ve written have been about breaches and one of the key components of any good attack is solid reconnaissance. An adversary with a clear understanding of a company’s staff can leverage that to get a much more complete picture than any port scan or pin-point key human targets to exploit. Plenty of penetration testers [2] use social media to devastating effect and so do real adversaries.  
Some of you reading this will be thinking:
A) Pah! I don’t use an form of social media so I’m safe
B) Meh, I’d never fall for any of that shenanigans, I’m too paranoid/security-minded
C) Mu-ha-ha! I use the Lynx text only browser [3] – what is this wide wide web you speak off?
Well, how about the person next to you or head of HR or the CEO? This blog post [4] illustrates a very smart, well thought out and executed social engineering attack using LinkedIn. LinkedIn have a very responsive security team and here’s one way to alert than of bogus profiles[5] should you ever run in to one, but would most people pick up on a fake profile?
I’ll leave you with this question: How would you and your security policies counter a targeted attack like that against a senior board member?

Chris Mohan --- Internet Storm Center Handler on Duty

1 comment(s)
ISC StormCast for Friday, January 24th 2014


Diary Archives