A yearlong phishing campaign used various techniques, including Morse code in some cases, to help evade security tools. Hackers created realistic-looking phishing emails that appear to resemble invoices with Microsoft Excel spreadsheets attached. If a user opened one of these malicious attachments, the group behind the attack could harvest their Office 365 credentials as well as other details, such as the device’s specific IP address and location. Researchers also found the attackers broke the HTML files into multiple segments, which helped make the code look benign to security tools and avoid detection.”]
Source: https://www.bankinfosecurity.com/microsoft-details-yearlong-office-365-phishing-campaign-a-17292