On Friday, April 19th, Microsoft sent letters to some of its e-mail users that their accounts may have been accessed by “individuals outside Microsoft” over the past three months.
The letter, reproduced on a Reddit forum, noted that the breaches happened between Jan. 1 and March 28 of this year because “a Microsoft support agent’s credentials were compromised.” The outside parties were able to view things like the e-mail addresses of the user and those they communicated with, as well as folder names and subject-line content.
Microsoft had suggested in its letter that the attackers could not read the contents of peoples’ e-mails. However, it later backtracked on that statement. So far, there appears to be no general information about the breach published by Microsoft, apart from the letter it sent to affected users.
Login credentials weren’t exposed, according to Microsoft’s letter. It nevertheless recommended that affected e-mail users should “reset your passwords” and be wary of getting e-mails with misleading domain names.
Microsoft told TechCrunch that “a limited number of consumer accounts were impacted, and we have notified all impacted customers.” According to a weekend TechCrunch story, no business customers were affected but indicated that Hotmail, MSN and Outlook accounts were affected and the attackers could access e-mail content. Although not confirmed, the possible motivation of the attackers was to gain access to account recovery information in order to unlock stolen iPhones.
In response, Microsoft confirmed that the attackers had gained access to the e-mail contents of some users, but that just six percent of the total was so affected. Another source indicated that the attackers had access for six months, in contrast to the three months claimed by Microsoft.
Microsoft isn’t disclosing how many accounts were affected by the breach, but it disabled the compromised support representative’s credentials to block further attacker access.
Why Does This Mean?
Targeting a privileged account, such as an account held by a Microsoft support agent, is a common tactic of attackers. Compromise of privileged accounts is a widespread and effective method among cybercriminals to get to the crown jewels very quickly and at low cost. It is, however, quite surprising that such a reputable company like Microsoft has reportedly not reacted to these anomalies for as long as three months.
In the meantime, whether you were contacted by Microsoft or not, its recommended that all Hotmail, MSN and Outlook Online users change their passwords and secret questions, as well as passwords for any other accounts that sent, or could have sent, a password recovery link to their Outlook Online email.
