Defending Against Direct Authentication Attacks in Microsoft Office 365

Whilst conducting security testing and assurance activities, I went looking to show logon events in Office 365. My first query was on IdentityEvents, this led to a view of a multi month attack by a threat actor/s against a tenent, followed by exploring the rabbit hole of logs and computer systems. This blog summarises some of the methods and findings when considering threat hunting and authentication defences for Office 365. (bear with me I am tired so this might need a bit of a tune up later!)

Guides

Enable Number Matching in Azure MFA

Introduction

MFA was the “silver bullet” but friction and security kind of go hand in hand, the idea of a push notification and simple “authorise” is great in theory, but in practise it is vulnerable to brute force and human error. In this post we are going to check out enabling number matching authentication in Azure.

This is just one configuration option, as you can see there are loads of options for methods and specific configurations. Bear in mind the pros and cons for each one, for example SMS based 2FA can be vulnerability to SIM swapping attacks. I’m going to focus on Number Matching in Authenticator for this post: Read more “Enable Number Matching in Azure MFA” →