ZeroFont

Cloud Security company Avanan has discovered a flaw in the Microsoft Office 365 platform that allows phishing attacks to bypass email filters. This technique, known as ZeroFont, fools the Microsoft natural language processing used to identify emails as malicious by inserting random text throughout the email, breaking up text strings that would be flagged. The random text embedded within the HTML code has a font size of zero, rendering the text invisible to the email recipient. This technique makes it possible to display different messages to the anti-phishing filters and to the email recipient. 

The NJCCIC recommends all users and administrators of Office 365 review the Avananreport on ZeroFont and educate end users about this and similar threats, reminding them never to click on links delivered in unexpected or unsolicited emails, especially to visit websites requiring the input of account credentials. Users who receive unexpected or unsolicited email requests from known senders inviting them to click on a link or open an attachment should always verify the sender via another means of communication before taking any action.