Microsoft is warning of cyber assault campaigns that abuse professional file internet hosting companies comparable to SharePoint, OneDrive, and Dropbox which might be extensively utilized in enterprise environments as a protection evasion tactic.
The top aim of the campaigns are broad and various, permitting risk actors to compromise identities and units and conduct enterprise electronic mail compromise (BEC) assaults, which in the end end in monetary fraud, information exfiltration, and lateral motion to different endpoints.
The weaponization of professional web companies (LIS) is an more and more in style danger vector adopted by adversaries to mix in with professional community site visitors in a way such that it typically bypasses conventional safety defenses and complicates attribution efforts.
The method can be referred to as living-off-trusted-sites (LOTS), because it leverages the belief and familiarity of those companies to sidestep electronic mail safety guardrails and ship malware.
Microsoft stated it has been observing a brand new development in phishing campaigns exploiting professional file internet hosting companies since mid-April 2024 that contain information with restricted entry and view-only restrictions.
Such assaults typically start with the compromise of a consumer inside a trusted vendor, leveraging the entry to stage malicious information and payloads on the file internet hosting service for subsequent sharing with a goal entity.
“The information despatched via the phishing emails are configured to be accessible solely to the designated recipient,” it stated. “This requires the recipient to be signed in to the file-sharing service — be it Dropbox, OneDrive, or SharePoint — or to re-authenticate by getting into their electronic mail tackle together with a one-time password (OTP) obtained via a notification service.”
What’s extra, the information shared as a part of the phishing assaults are set to “view-only” mode, stopping the flexibility to obtain and detect embedded URLs inside the file.
A recipient who makes an attempt to entry the shared file is then prompted to confirm their identification by offering their electronic mail tackle and a one-time password despatched to their electronic mail account.
As soon as they’re efficiently approved, the goal is instructed to click on on one other hyperlink to view the precise contents. Nonetheless, doing so redirects them to an adversary-in-the-middle (AitM) phishing web page that steals their password and two-factor authentication (2FA) tokens.
This not solely permits the risk actors to grab management of the account, but additionally use it to perpetuate different scams, together with BEC assaults and monetary fraud.
“Whereas these campaigns are generic and opportunistic in nature, they contain subtle strategies to carry out social engineering, evade detection, and increase risk actor attain to different accounts and tenants,” the Microsoft Risk Intelligence workforce stated.
The event comes as Sekoia detailed a brand new AitM phishing equipment referred to as Mamba 2FA that is offered as phishing-as-a-service (PhaaS) to different risk actors to conduct electronic mail phishing campaigns that propagate HTML attachments impersonating Microsoft 365 login pages.
The equipment, which is obtainable on a subscription foundation for $250 monthly, helps Microsoft Entra ID, AD FS, third-party SSO suppliers, and client accounts. Mamba 2FA has been actively put to make use of since November 2023.
“It handles two-step verifications for non-phishing-resistant MFA strategies comparable to one-time codes and app notifications,” the French cybersecurity firm stated. “The stolen credentials and cookies are immediately despatched to the attacker by way of a Telegram bot.”
