The GreatFire.org group, which monitors China's Internet surveillance and censorship system, reports that over the weekend, Outlook.com email service was attacked by man-in-the-middle type.
While the web interface was not affected, it was the case for Microsoft's IMAP and SMTP email services. Emails sent and received by Chinese users via a software client could thus be spied on.
The attack lasted for almost a day before ending with a fraudulent electronic certificate which usurped the identity of Microsoft. Users were alerted by an error message in the email client at the start of the attack.
However, the risk exists that they simply ignored it especially since this kind of message is less dissuasive compared to a display in the browser and can simply suggest a connection problem. An example below (offered by GreatFire.org) with the iPhone default email client on the left and an alert in Firefox on the right:
GreatFire.org suspects the Chinese authorities of being behind this cyber attack or of having permitted it. It comes after the complete blocking of access to Gmail at the end of 2014. In October, it was Apple's iCloud service which was the victim of a man-in-the-middle attack.
For the moment, Microsoft only indicates that a small number of users have been affected by malicious routing to a server impersonating Outlook.com. " If a user sees a certificate alert, they should contact their Internet service provider for assistance. "