I was alerted to this by an article on The Register which points to the Godai Group‘s investigation into what happens when you register domains “close” to a reputable company and grab all the emails that happen to pop by. It is hardly a surprise to anyone who has run an email system, but you will get tons of email delivered caused by email address typos. Specifically Godai Group looked at a specific type of typo – accidentally leaving out a “.”. For example, one of the domains that the Godai Group picked up on was email@example.com where “someone” has registered caibm.com (no dot) … whether or not that person is sniffing those emails cannot be known, but they could.
Again, to those who have run email systems it is no surprise to learn that some of the emails contain “interesting” information not limited to :-
- Trade secrets
- Business invoices
- Personal information about employees
- Usernames and passwords!
- Network diagrams.
What is not mentioned is that those Fortune 500 companies almost certainly have policies in place prohibiting acts such as sending passwords and other sensitive information by email. But of course there is a description for someone who reads all of the corporate policies – someone who isn’t doing their job!
There is an interesting list of mitigations in the Godai Group report, but it could be a lot more extensive :-
- When sending out an email to an address where the left hand side would be a valid internal address, flag the destination in your logs. Use that information to build up a list of domains for which you should check for valid internal addresses and freeze (hold in the queue) any messages that match. As an example, if firstname.lastname@example.org were a valid address you might want to freeze any emails addressed to email@example.com.
- Use your email logs to build up a database of domains that you send email to. This will allow you to identify similar domains that may be practicing so-called “doppleganger domains” that you may want to take some action against. You may think you can guess what the domains would be, but there is a lot to be said for hard evidence.
- Perform content filtering on outgoing email, and build up a set of rules to catch emails containing patterns that match certain kinds of emails you do not want leaving your organisation – to begin with a pattern matching “password [is] XXXXXX”. This could take considerable effort to build, and there will always be the chance of a false positive so you will want a sensible warning message when emails matching the relevant content filter get caught – “Please check that this email does not contain confidential information; please check the recipient address, and if necessary re-phrase the email”.
- Encourage the use of end-to-end encryption such as PGP. Plain encryption is not sufficient – “walled garden” email systems such as GroupWise support encryption for internal emails, but this is about external (even if it isn’t intentionally so) email which is not encrypted with such corporate email systems. In fact systems such as GroupWise may be considered dangerous in this context – it comes with the word encryption on the tin, and even allows you to “take back” emails that you have sent that you regret. These facilities encourage dangerous practices.
- Education, education, education. But this will not accomplish much – not only are the people who really need to be educated not listening, but these problems are mistakes – both in terms of accidentally sending emails to the wrong address, and in terms of emailing information that should probably not be sent via email.
- Lastly, and perhaps for amusement value, you could try persuading senior managers that the danger of them sending inappropriate information accidentally out to third parties via email is so great that it justifies setting up a process by which all their email sent to external address is manually reviewed to ensure that it is not an accidental release of internal information. Good luck on that one!