Microsoft is warning of cyber assault campaigns that abuse official file internet hosting companies equivalent to SharePoint, OneDrive, and Dropbox which are broadly utilized in enterprise environments as a protection evasion tactic.
The top objective of the campaigns are broad and assorted, permitting menace actors to compromise identities and units and conduct enterprise electronic mail compromise (BEC) assaults, which in the end end in monetary fraud, knowledge exfiltration, and lateral motion to different endpoints.
The weaponization of official web companies (LIS) is an more and more widespread threat vector adopted by adversaries to mix in with official community visitors in a way such that it typically bypasses conventional safety defenses and complicates attribution efforts.
The strategy can be known 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 pattern in phishing campaigns exploiting official file internet hosting companies since mid-April 2024 that contain recordsdata 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 recordsdata and payloads on the file internet hosting service for subsequent sharing with a goal entity.
“The recordsdata 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 coming into their electronic mail handle together with a one-time password (OTP) acquired via a notification service.”
What’s extra, the recordsdata shared as a part of the phishing assaults are set to “view-only” mode, stopping the power 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 id by offering their electronic mail handle and a one-time password despatched to their electronic mail account.
As soon as they’re efficiently licensed, 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 menace 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 methods to carry out social engineering, evade detection, and increase menace actor attain to different accounts and tenants,” the Microsoft Menace Intelligence staff stated.
The event comes as Sekoia detailed a brand new AitM phishing equipment known as Mamba 2FA that is bought as phishing-as-a-service (PhaaS) to different menace 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 per 30 days, 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 equivalent to one-time codes and app notifications,” the French cybersecurity firm stated. “The stolen credentials and cookies are immediately despatched to the attacker through a Telegram bot.”