A new phishing campaign was discovered by ISC Handler Xavier Mertens and the campaign seems to still be active.

The phishing emails look very like legitimate Office 365 non-delivery alerts and include Office 365 branding. As is the case with official non-delivery alerts, the user is warned that messages have not been delivered and told that action is required.

The Office 365 phishing emails state that “Microsoft found Several Undelivered Messages” and attributes the non-delivery to “Server Congestion.” The emails request the sender to retype the recipient’s email address and send the message again, although conveniently they include a Send Again button.

If users use the Send Again button, they will be sent to a website that closely resembles the official Office 365 website and includes a login box that has been auto-populated with the user’s email address.

If the password is typed, a JavaScript function sends both the email address and password to the hacker. The user will then be sent to the genuine outlook.office365.com website where they will be shown a real Office 365 login box.

While the Office 365 phishing emails and the website look genuine, there are signs that all is not what it seems. The emails are well composed and the sender’s email – postmaster@us.ibm.com – looks official but there is irregular capitalization of the warning message: Something that would not happen on an official Microsoft notification.

The clearest indication that this is a phishing scam is the domain to which users are sent if they click on the Send Again button. It is not an official Microsoft domain (agilones.com).

While the mistake in the email may be overlooked, users should notice the domain, although some users may proceed and type passwords as the login box is identical to the login on the official Microsoft site.

The campaign shows just how vital it is to carefully check every message before taking any action and to always review the domain before disclosing any sensitive data.

Hackers use Office 365 phishing emails because so many companies have signed up to use Office 365. Mass email campaigns therefore have a high chance of reaching an Outlook inbox. That said, it is easy to target office 365 users. A business that is using Office 365 broadcasts it using their public DNS MX records.

Firms can improve their resilience to phishing attacks through mandatory security awareness training for all workers. Employees should be told to always review messages carefully and should be guided how to identify phishing emails.

Companies should also ensure they have an advanced spam filtering solution set up. While Microsoft does offer anti-phishing protection for Office 365 through its Advanced Threat Protection (APT) offering, companies should consider using a third-party spam filtering solution with Office 365.

SpamTitan supplies superior protection against phishing and zero-day attacks, an area where APT is not proficient.