We recently ran an internal EntraIDiots CTF where players had to phish a user, register a device, grab a PRT, and use that to enroll Windows Hello for Business—because the only way to access the flag site was via phishing-resistant MFA.

The catch? To make WHFB registration work, the victim must have performed MFA in the last 10 minutes.In our CTF, we solved this by forcing MFA during device code flow authentication. But that’s not something you can do in a real-life red team scenario.

So we asked ourselves: how can we force a user we do not controlll to always perform MFA? That’s exactly what this blog explores.