Microsoft recently discovered a widespread phishing attack campaign targeting Office 365 users that lures victims to a phony Office authentication page where it pilfers their credentials and later executes a second wave of attack, business email compromise (BEC), using intel gathered from their email accounts.
The attackers behind the campaign have targeted more than 10,000 organizations since September 2021, according to Microsoft, and employ the Evilginx2 phishing kit as the infrastructure for hijacking the authentication process. “We also uncovered similarities in their post-breach activities, including sensitive data enumeration in the target’s mailbox and payment frauds,” according to a post by the Microsoft 365 Defender Research Team that details the attacks.
The man-in-the-middle attack — or, as Microsoft now calls it, adversary-in-the-middle (AiTM) — sets up a proxy server that sits between the victim and the actual authentication page. “Such a setup allows the attacker to steal and intercept the target’s password and the session cookie that proves their ongoing and authenticated session with the website. Note that this is not a vulnerability in MFA; since AiTM phishing steals the session cookie, the attacker gets authenticated to a session on the user’s behalf, regardless of the sign-in method the latter uses,” Microsoft said in its post.
Organizations should up their MFA game with conditional access policies, which vet sign-in requests based on identity, IP location, and device status, for example, according to Microsoft.