{"id":135958,"date":"2024-10-08T09:00:00","date_gmt":"2024-10-08T16:00:00","guid":{"rendered":"https:\/\/www.microsoft.com\/en-us\/security\/blog\/?p=135958"},"modified":"2024-10-08T10:37:08","modified_gmt":"2024-10-08T17:37:08","slug":"file-hosting-services-misused-for-identity-phishing","status":"publish","type":"post","link":"https:\/\/www.microsoft.com\/en-us\/security\/blog\/2024\/10\/08\/file-hosting-services-misused-for-identity-phishing\/","title":{"rendered":"File hosting services misused for identity phishing"},"content":{"rendered":"\n

Microsoft has observed campaigns misusing legitimate file hosting services increasingly use defense evasion tactics involving files with restricted access and view-only restrictions. While these campaigns are generic and opportunistic in nature, they involve sophisticated techniques to perform social engineering, evade detection, and expand threat actor reach to other accounts and tenants. These campaigns are intended to compromise identities and devices, and most commonly lead to business email compromise (BEC) attacks to propagate campaigns, among other impacts such as financial fraud, data exfiltration, and lateral movement to endpoints.<\/p>\n\n\n\n

Legitimate hosting services, such as SharePoint, OneDrive, and Dropbox, are widely used by organizations for storing, sharing, and collaborating on files. However, the widespread use of such services also makes them attractive targets for threat actors, who exploit the trust and familiarity associated with these services to deliver malicious files and links, often avoiding detection by traditional security measures.<\/p>\n\n\n\n

Importantly, Microsoft takes action against malicious users violating the Microsoft Services Agreement<\/a> in how they use apps like SharePoint and OneDrive. To help protect enterprise accounts from compromise, by default both Microsoft 365 and Office 365 support multi-factor authentication (MFA)<\/a> and passwordless sign-in. Consumers can also go passwordless<\/a> with their Microsoft account. Because security is a team sport, Microsoft also works with third parties like Dropbox to share threat intelligence and protect mutual customers and the wider community.<\/p>\n\n\n\n

In this blog, we discuss the typical attack chain used in campaigns misusing file hosting services and detail the recently observed tactics, techniques, and procedures (TTPs), including the increasing use of certain defense evasion tactics. To help defenders protect their identities and data, we also share mitigation guidance to help reduce the impact of this threat, and detection details and hunting queries to locate potential misuse of file hosting services and related threat actor activities. By understanding these evolving threats and implementing the recommended mitigations, organizations can better protect themselves against these sophisticated campaigns and safeguard digital assets.<\/p>\n\n\n\n

Attack overview<\/h2>\n\n\n\n

Phishing campaigns exploiting legitimate file hosting services have been trending throughout the last few<\/a> years<\/a>, especially due to the relative ease of the technique. The files are delivered through different approaches, including email and email attachments like PDFs, OneNote, and Word files, with the intent of compromising identities or devices. These campaigns are different from traditional phishing attacks because of the sophisticated defense evasion techniques used.<\/p>\n\n\n\n

Since mid-April 2024, we observed threat actors increasingly use these tactics aimed at circumventing defense mechanisms:<\/p>\n\n\n\n