Hackers breached Microsoft email services (Outlook.com, Hotmail, MSN) and accessed user accounts after compromising a support agent’s credentials, Microsoft has confirmed.
In a breach notification sent to impacted users, the software giant revealed that hackers had access to its email services for roughly three months this year, between January 1 and March 28.
Microsoft informed users that, following the compromise, “individuals outside Microsoft” were able to access information within the users’ Microsoft email accounts, including the email addresses, subjects of emails, and contact names.
“This unauthorized access could have allowed unauthorized parties to access and/or view information related to your email account (such as your email address, folder names, the subject lines of emails, and the names and email addresses you communicate with), but not the content of any emails or attachments,” Microsoft told users.
Responding to a SecurityWeek inquiry, Microsoft said the attack affected only a limited subset of customer accounts and that the scheme has been already addressed by blocking the attackers’ access. The company, however, did not say how many were impacted.
Around 6% of the affected individuals were notified that the attackers could have had unauthorized access to the content of their email accounts. Microsoft has provided these users with additional guidance and support and also increased detection and monitoring for them.
In its initial notification, Microsoft also told affected users that their login credentials were not directly impacted by the hack, but the software company did advise for a password change.
The company also warns that, given that account-related information has been accessed, chances are that the affected users will experience email phishing attacks or other types of spam emails.
“Even though login credentials were not affected, users should consider changing their passwords and enabling multi-factor authentication features if they have not already. All users should make sure to check the sender’s email addresses of emails they receive to make sure they are legitimate,” Robert Vamosi, senior product marketing manager at ForgeRock, told SecurityWeek in an emailed comment.
According to Motherboard, the hackers actually had full access to email content, because the Microsoft support account they compromised belonged to a privileged user.
“There’s no doubt that Microsoft is scrambling to find out how the credentials were compromised, and to make changes so it doesn’t happen again,” Tim Erlin, VP of product management and strategy at Tripwire, told SecurityWeek.
“No organization is infallible when it comes to cybersecurity. […] these types of incidents should really force every organization to evaluate how they’ve implemented their own security controls. There’s a reason that incident response is part of cybersecurity. Prevention is the ideal, but compromise remains the reality,” Erlin continued.
Related: Office 365, Outlook Credentials Most Targeted by Phishing Kits
Related: Attackers Are Landing Email Inboxes Without the Need to Phish