How Easy Is It to Take Over a Microsoft 365 Account?

Is MFA enough to secure a Microsoft 365 account?

“We have MFA, so our Microsoft 365 accounts are secure” is something I hear very often in companies.

Enabling multi-factor authentication is an important security measure, but it does not automatically mean that an employee account is effectively protected against takeover.

In practice, a cybercriminal does not need to try to crack the password. It is much easier to convince the user to provide the required information themselves.

The employee receives an email containing a link. After clicking it, they are taken to a page that looks almost identical to the Microsoft 365 sign-in screen. The logo matches, the form looks familiar, and the browser shows a padlock. The difference may be hidden in the website address and may be subtle enough that the user does not notice it during normal work.

They enter their username and password. Then a request for additional authentication appears. The user completes the next step because they are convinced they are signing in to a legitimate Microsoft service.

And that is exactly when access to the account may be taken over.

Video language: Polish (English subtitles available).

What Does a Microsoft 365 Account Takeover Look Like?

In the video below, I show step by step what a phishing attack against a Microsoft 365 user may look like. The material was created to demonstrate the attack mechanism in practice - from the perspective of an ordinary employee performing actions that look like a standard sign-in to corporate email.

I discuss an Adversary-in-the-Middle (AiTM) attack scenario. In this type of attack, a cybercriminal attempts to position themselves between the user and the legitimate Microsoft service. The goal does not have to be limited to obtaining the username and password.

The attack may also lead to the interception of the user's authenticated session.

A company may have MFA enabled, and the employee may correctly complete additional authentication. However, this does not automatically mean that every possible sign-in method and every attack scenario have been adequately secured.

MFA alone is not the entire Microsoft 365 security system. In the video, I show:

• how a user can end up on a fake Microsoft 365 sign-in page,
• why a padlock in the browser does not mean that a website is legitimate,
• how phishing can lead to an account takeover,
• why not every MFA method provides the same level of protection,
• the importance of Conditional Access and Microsoft Entra ID,
• why it is worth regularly reviewing sign-in logs,
• why it is worth regularly reviewing sign-in logs,

Microsoft 365 security does not end with MFA.

What matters most, however, is looking at the entire attack process.

An employee usually does not manually type the address of a fake Microsoft 365 website into the browser.

Someone first has to convince them to open it. Very often, the entire incident begins with a carefully crafted phishing message.

That is why Microsoft 365 security should not be reduced to a single setting or a single technology.

Protection should include email security and phishing filtering, identity configuration in Microsoft Entra ID, appropriate Conditional Access policies, suitable authentication methods, device security, and analysis of what is actually happening in the environment.

If your company uses Microsoft 365 and already has MFA enabled, it is worth checking more than just whether it is turned on.

Check how users actually sign in to Microsoft 365, which policies are enforced during those sign-ins, and whether the authentication methods being used are resistant to modern phishing scenarios.