E-Mail security breaches: A cautionary tale.

This past week, I heard from a business colleague who heads up a firm that operates in the IT sector. It isn’t a large company, but its business is international in scope and its entire employee workforce would certainly be considered tech-savvy.

Nevertheless, the company suffered a serious security breach affecting its e-mail system … and it took nearly one week of investigation, diagnosis and repair to deal with the fallout. Ultimately, the system was secured with everything restored and running again, but it took much longer than  expected.

What had happened was that an unknown attacker obtained the user ID and password for one of the company’s e-mail accounts, and used those credentials to log on to the mail system as the legitimate user. The attacker then changed the contact name on the account to a fake U.S. telephone number – we’ll call it “+1(4XX) 6XX-9XXX” – and launched a program from his/her/its host computer (hosted by Microsoft and located in in a different country than the affected user) which sent out thousands of e-mails having the subject “Missed call from +1(4XX) 6XX-9XXX” and an attachment that looked like a harmless audio file containing a voicemail message.

This type of phishing attack is well-known, and it would be dangerous to open the attachment (no one at the company attempted to do so). The company’s e-mail server eventually blocked the account because it exceeded the maximum outgoing e-mail limit, but strangely enough the administrator was never notified of this fact. The company only discovered the breach after the user called in to complain about receiving thousands of “failed delivery” messages. It took the better part of a full business day just to piece together what was going on, and why.

The attacker also installed a rule on the compromised account which moved all incoming email to an obscure folder. The rule was cleverly disguised, making it easy to overlook and hence more time-consuming to find and remove.

This friend advised that there are a number of “lessons learned” from his company’s experience, which should be considered for implementation by businesses of all sizes everywhere:

1. Implement security policies requiring strong passwords (big, long, hard-to-guess ones) and frequent password changes (once every 90 days or more frequently). In the case of this particular company, its password strength policy was up to snuff but it wasn’t enforcing rotation. That changed immediately after the breach.

2.  Require multi-factor authentication (MFA). This is where a user doesn’t merely enter a password to log on, but also has to enter a one-time code sent via SMS or a smartphone app. It’s inconvenient, but regrettably it’s the world we live in today. In the case of this particular company, it hadn’t been using MFA. They are now.

3.  Be vigilant in reminding users NEVER to click on links or file attachments embedded in received e-mails unless they absolutely trust the sender. Some larger companies have “drills” which broadcast fake phishing emails to their employees. Those who click are identified and sent to “dum-dum school” for remedial training.

Failing that, companies should adopt policies wherein any employee who receives anything via e-mail that looks like particularly clever or tempting phishing, to notify the company about it immediately for investigation.

4.  Discourage users from logging on to their mail accounts from public locations using unencrypted WiFi. It’s easy to sniff WiFi signals and it’s even easier to read the data in unencrypted signals, which appear as plain text. Typically, if the WiFi connection requires a passphrase to be entered in order to connect, then it’s encrypted WiFi. If not … watch out.

5.  Monitor the e-mail server at least once each day to discover any security breaches or threats, since those servers may not always notify administrators automatically. The sooner a problem is discovered, the quicker and easier it will be to contain and kill it.

6.  Require users to archive messages in their Inbox and Sent Items folders regularly.  The moment an attacker is able to access an account, he/she/it can easily retrieve and quickly download all the messages on the server, and those messages could contain confidential or sensitive data. Therefore, taking this action will move those messages to each user’s device and purge them from the central server.

I’m thankful that my friend was willing to share his experience and suggestions for how to avoid a similar breach happening at my own company. Based on the “lessons learned,” we performed an audit of our own procedures and made several adjustments to our protocols as a result – small changes with potentially large consequences.  I suggest you do the same.