Phishing Campaign Identified Targeting Office 365 Admins

A new phishing campaign has been detected that is targeting Office 365 admins, whose accounts are far more valuable to cybercriminals than standard Office 365 accounts.

A standard Office 365 email account can used for spamming or conducting further phishing attacks on the organization or business contacts. However, there is a problem. When the account is used for phishing, the sent messages are likely to be noticed by the user. Failed delivery messages will also arrive in the user’s inbox. The account may only be able to be used for a short time before an account compromise is detected.

The attackers targeting Office 365 admins aim to compromise the entire domain. Office 365 admins can create new accounts on the domain, which are then used for phishing. Since the only person using that account is the attacker, it is likely the malicious actions will not be noticed, at least not as quickly. The only person who will see the failed delivery messages and sent emails is the attacker.

The newly created account abuses trust in the business domain. Any individual to receive such a phishing message may mistakenly believe the email is a legitimate message from the company. The messages also take advantage of the reputation of a business. Since the business domain will have been used only to send legitimate messages, the domain will have a high trust score. That makes it far more likely that the emails being sent from the new account will be delivered to inboxes and will not be picked up by Office 365 spam filters. The Office 365 admin may also have access to all email accounts on the domain, which will allow the attacker to steal a huge amount of email data.

In theory, Office 365 admins should be better at identifying phishing emails than other employees in the organization as they usually work in the IT department; however, these emails are very realistic and will likely fool many Office 365 admins.

The lure being used is credible. The emails appear to have been sent by Microsoft and include the Microsoft and Office 365 logos. The emails claim that the organization’s Office 365 Business Essentials invoice is ready. The user is told to sign into the Office 365 admin center to update their payment information, set their Message Center preferences, and edit their release preferences or join First Release and set these up if they have not done so already. The emails include an unsubscribe option and are signed by Microsoft and include the correct contact information. The emails also link to Microsoft’s privacy statement.

The embedded hyperlinks in the emails link to an attacker-controlled domain that is a carbon copy of the official Microsoft login page. If the user’s credentials are entered, they are captured by the attacker.

This campaign highlights how important it is to have layered email security defenses in place to block phishing attacks. Many phishing emails bypass standard Office 365 anti-phishing controls so additional protection is required.

An advanced anti-phishing solution such as SpamTitan should be layered on top of Office 365 to provide greater protection against sophisticated phishing attacks. Approximately 25% of all phishing emails bypass standard Office 365 phishing protections.

Another anti-phishing layer that many businesses have yet to implement is a web filter. A web filter, such as WebTitan, provides protection when messages are delivered to inboxes, as it blocks attempts by employees to visit phishing websites. When a link to a known phishing website is clicked, or the user attempts to visit a questionable domain, they will be directed to a block page and the phishing attack will be blocked.