From cookie theft to BEC: Attackers use AiTM phishing sites as entry point to further financial fraud


A large-scale phishing campaign that used adversary-in-the-middle (AiTM) phishing sites stole passwords, hijacked a user’s sign-in session, and skipped the authentication process even if the user had enabled multifactor authentication (MFA). The attackers then used the stolen credentials and session cookies to access affected users’ mailboxes and perform follow-on business email compromise (BEC) campaigns against other targets. Based on our threat data, the AiTM phishing campaign attempted to target more than 10,000 organizations since September 2021.

Phishing remains to be one of the most common techniques attackers use in their attempts to gain initial access to organizations. According to the 2021 Microsoft Digital Defense Report, reports of phishing attacks doubled in 2020, and phishing is the most common type of malicious email observed in our threat signals. MFA provides an added security layer against credential theft, and it is expected that more organizations will adopt it, especially in countries and regions where even governments are mandating it. Unfortunately, attackers are also finding new ways to circumvent this security measure.

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Source: Microsoft 365 Defender Research Team/MSTIC